bluuebunny/crossref_metadata_2025 huggingface dataset:
A Hydrophobic Mutant of
Rhizobium etli
Altered in Nodulation Competitiveness and Growth in the Rhizosphere
Authors: Araujo Ricardo S. , Robleto Eduardo A. , Handelsman Jo
Published: January 2020

We isolated and characterized CE3003, a Tn
5
-induced mutant with altered colony morphology derived from
Rhizobium etli
CE3. CE3003 produced domed colonies and was highly hydrophobic as indicated by its ability to partition into hexadecane, whereas its parent produced flat colonies and was hydrophilic. On bean plants, CE3003 induced nodules and reduced acetylene. CE3003 and CE3 grew at similar rates when they were grown separately or together in culture medium or inoculated singly onto bean seeds. However, when they were mixed at a 1:1 ratio and applied to seeds, CE3003 achieved significantly lower populations than CE3 in the rhizosphere. Five days after coinoculation of CE3 and CE3003, the population of the mutant was less than 10% of the population of CE3 in the bean rhizosphere. To determine the nodulation competitiveness of the mutant, it was coinoculated with CE3 at various ratios at planting, and the ratio of the nodules occupied by each strain was determined 21 days later. A 17,000-fold excess of CE3003 in mixed inocula was required to obtain equal nodule occupancy by the two strains. A genomic library of strain CE3 was mobilized into CE3003, and we identified a cosmid, pRA3003, that restored the parental colony morphology and hydrophilicity to the mutant. Restoration of the parental colony morphology was accompanied by recovery of the ability to grow competitively in the rhizosphere and to compete for nodulation of beans. The data show an association between cell surface hydrophobicity, nodulation competitiveness, and competitive growth in the rhizosphere in mutant CE3003.
Vitamin B12 production by Citrobacter freundii or Klebsiella pneumoniae during tempeh fermentation and proof of enterotoxin absence by PCR
Authors: Keuth S , Bisping B
Published: January 2020

The influence of some fermentation parameters on vitamin B12 formation by strains of Citrobacter freundii and Klebsiella pneumoniae isolated from Indonesian tempeh samples during tempeh fermentation was investigated. A decrease in fermentation temperature from 32 to 24 degrees C led to a decrease in vitamin B12 formation. Inoculation of soybeans with different numbers of cells of C. freundii at the beginning of solid-substrate fermentation showed that only the velocity of vitamin formation and not the final amount of vitamin formed depended on the number of cells. The addition of cobalt and 5,6-dimethylbenzimidazole increased the vitamin B12 content of tempeh. Nevertheless, levels of incorporation of the two precursors into the vitamin B12 molecule were very low. Neither C. freundii nor K. pneumoniae possessed the genes encoding the enterotoxins Shiga-like toxin SLT IIA, heat-labile enterotoxin LT Ih, and heat-stable enterotoxin ST Ih, as indicated by PCR. This result supports the suggested use of these two strains to form vitamin B12 during tempeh fermentation in Indonesia.
Reduction of Cr(VI) by a Consortium of Sulfate-Reducing Bacteria (SRB III)
Authors: Fude Li , Harris Bob , Urrutia Matilde M. , Beveridge Terry J.
Published: January 2020

A consortium of bacteria with tolerance to high concentrations of Cr(VI) (up to 2,500 ppm) and other toxic heavy metals has been obtained from metal-refinishing wastewaters in Chengdu, People's Republic of China. This consortium consists of a range of gram-positive and gram-negative rods and has the capacity to reduce Cr(VI) to Cr(III) as amorphous precipitates which are associated with the bacterial surfaces. An endospore-producing, gram-positive rod and a gram-negative rod accumulate the most metallic precipitates, and, over time, 80 to 95% of Cr can be removed from concentrations ranging from 50 to 2,000 ppm (0.96 to 38.45 mM). Kinetic studies revealed a first-order constant for Cr removal of 0.1518 h
-1
for an initial concentration of 1,000 ppm (19.3 mM), and the sorption isothermal data could be interpreted by the Freundlich relationship. The sorption was not entirely due to a passive interaction with reactive sites on the bacterial surfaces since gamma-irradiated, killed cells could not immobilize as much metal. When U or Zn was added with the Cr, it was also removed and could even increase the total amount of Cr immobilized. The consortium was tolerant to small amounts of oxygen in the headspace of tubes, but active growth of the bacteria was a requirement for Cr immobilization through Cr(VI) reduction, resulting in the lowering of E
h
. Our data suggest that the reduction was via H
2
S. This consortium has been named SRB III, and it may be useful for the bioremediation of fluid metal-refining wastes.
Application of multilocus enzyme electrophoresis and restriction fragment length polymorphism analysis to the typing of Listeria monocytogenes strains isolated from raw milk, nondairy foods, and clinical and veterinary sources
Authors: Harvey J , Gilmour A
Published: January 2020

The powerful discriminatory typing capabilities of multilocus enzyme electrophoresis and restriction fragment length polymorphism analysis were applied to Listeria monocytogenes strains from raw milk, nondairy foods, and clinical and veterinary sources. The raw milk and nondairy food strains were sequential isolates obtained over a year-long period from a number of different producers and manufacturers. Results obtained by the two typing methods were in substantial agreement and showed that both raw milk and nondairy foods frequently contain recurrent L. monocytogenes strains, thus suggesting that the presence of these organisms in such commodities often arises because of contamination from within their respective processing environments. Most recurrent strains were serogroup 1/2, with only one instance of recurrent serogroup 4 strains. Some recurrent L. monocytogenes strains, including the serogroup 4 strains, were found by analysis of multilocus enzyme electrophoresis results to be closely related to clinical and veterinary strains, thus suggesting that strains adapted for survival in the food-processing environment retain their potential for pathogenicity.
Utilization of Organic Nitrogen Sources by Two Phytoplankton Species and a Bacterial Isolate in Pure and Mixed Cultures
Authors: Ietswaart T. , Schneider P. J. , Prins R. A.
Published: January 2020

Algal production of dissolved organic carbon and the regeneration of nutrients from dissolved organic carbon by bacteria are important aspects of nutrient cycling in the sea, especially when inorganic nitrogen is limiting. Dissolved free amino acids are a major carbon source for bacteria and can be used by phytoplankton as a nitrogen source. We examined the interactions between the phytoplankton species
Emiliania huxleyi
and
Thalassiosira pseudonana
and a bacterial isolate from the North Sea. The organisms were cultured with eight different amino acids and a protein as the only nitrogen sources, in pure and mixed cultures. Of the two algae, only
E. huxleyi
was able to grow on amino acids. The bacterium MD1 used all substrates supplied, except serine. During growth of MD1 in pure culture, ammonium accumulated in the medium. Contrary to the expectation, the percentage of ammonium regenerated from the amino acids taken up showed no correlation with the substrate C/N ratio. In mixed culture, the algae grew well in those cultures in which the bacteria grew well. The bacterial yields (cell number) were also higher in mixed culture than in pure culture. In the cultures of MD1 and
T. pseudonana,
the increase in bacterial yield (number of cells) over that of the pure culture was comparable to the bacterial yield in mixed culture on a mineral medium. This result suggests that
T. pseudonana
excreted a more-or-less-constant amount of carbon. The bacterial yields in mixed cultures with
E. huxleyi
showed a smaller and less consistent difference than those of the pure cultures of MD1. It is possible that the ability of
E. huxleyi
to use amino acids influenced the bacterial yield. The results suggest that interactions between algae and bacteria influence the regeneration of nitrogen from organic carbon and that this influence differs from one species to another.
Monitoring of fecal pollution in coastal waters by use of rapid enzymatic techniques
Authors: Fiksdal L , Pommepuy M , Caprais M P , Midttun I
Published: January 2020

Enzyme assays for 4-methylumbelliferyl-beta-D-galactopyranosidase and 4-methylumbelliferyl-beta-D-glucuronidase activities were used for rapid detection (25 min) of fecal water pollution and to determine the impact of sewage discharge in coastal waters. Two coastal areas were investigated: (i) an estuary characterized by a high degree of contamination downstream of a discharge from a sewage treatment plant and a low degree of water renewal and (ii) a fjord with a low degree of pollution and a high degree of water renewal. Statistical analysis showed that a global correlation curve could be used to estimate concentrations of culturable fecal coliform bacteria in the two coastal areas, although environmental factors important for cell physiology (e.g., salinity) varied at different sampling locations. The sensitivity limit for detection of 4-methylumbelliferyl-beta-D-glucuronidase activity corresponded to bacterial concentrations on the order of 10 to 100 CFU/100 ml. The 4-methylumbelliferyl-beta-D-galactopyranosidase assay was less sensitive because of a higher rate of substrate autohydrolysis. The detection limit corresponded to bacterial concentrations on the order of 100 to 1,000 fecal coliforms per 100 ml.
Survival of lux-lac-marked biosurfactant-producing Pseudomonas aeruginosa UG2L in soil monitored by nonselective plating and PCR
Authors: Flemming C A , Leung K T , Lee H , Trevors J T , Greer C W
Published: January 2020

Two reporter systems, lacZY and luxAB, were stably integrated into the chromosome of Pseudomonas aeruginosa UG2, a biosurfactant-producing strain. Growth and rhamnolipid production of the UG2 wild-type and reporter gene-bearing UG2L strains were similar in liquid culture. A spontaneous rifampin-resistant detecting UG2Lr, allowed antibiotic selection. Phenotypic characteristics were compared for usefulness in detecting UG2Lr colonies: morphology, fluorescent pigment production, light emission (lux), X-Gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside) cleavage (lac), and rifampin resistance. Survival patterns of UG2, UG2L, and UG2Lr strains were similar in sandy loam soil microcosms over 12 12 weeks. The lac marker was not suitable for monitoring P. aeruginosa UG2Lr in soil since 20 to 42% of cultured, aerobic, heterotrophic soil microorganisms formed blue, lactose-positive colonies. The lux genes provided a stable and unequivocal reporter system, as effective as conventional antibiotic plating, for tracking microorganisms nonselectively at 10(3) CFU/g of soil. Three months after inoculation into oil-contaminated and uncontaminated soil microcosms, UG2Lr cells were recovered at 10(7) and 10(4) cells per g (dry weight) of soil, respectively. Detection by PCR amplification of part of the luxA gene confirmed a decrease in UG2Lr cell numbers in uncontaminated soil. In combination, antibiotic resistance, bioluminescence, and PCR analyses provided sensitive detection and quantitative enumeration of P. aeruginosa UG2Lr in soil.
Genetic analysis and overexpression of lipolytic activity in Bacillus subtilis
Authors: Dartois V , Coppée J Y , Colson C , Baulard A
Published: January 2020

The previously cloned Bacillus subtilis lipase gene (lip) was mapped on the chromosome and used in the construction of a B. subtilis derivative totally devoid of any lip sequence. Homologous overexpression was performed in this strain by subcloning the lip open reading frame on a multicopy plasmid under the control of a strong gram-positive promoter. A 100-fold overproducing strain was obtained, which should facilitate purification of the secreted protein. Furthermore, the delta lip strain BCL1050 constitutes an ideal host for the cloning of heterologous lipase genes.
Degradation of pyrene at low defined oxygen concentrations by a Mycobacterium sp
Authors: Fritzsche C
Published: January 2020

In a fermentor, a Mycobacterium sp. was grown on pyrene at defined oxygen concentrations in a range from 11.4 to 227 microM. The maximal growth rate (mumax = 0.057 h-1) and the dissolved oxygen half-saturation constant (KDO = 5.9 microM) were calculated. At 3.4 microM, the growth rate (mu = 0.011 h-1) was only half of what was expected from the kinetic data. Apparently, this was due to limitation of an oxygenase of pyrene degradation.
Optimization of the Sistrom Culture Medium for Large-Scale Batch Cultivation of
Rhodospirillum rubrum
under Semiaerobic Conditions with Maximal Yield of Photosynthetic Membranes
Authors: Ghosh R. , Hardmeyer A. , Thoenen I. , Bachofen R.
Published: January 2020

The defined medium A of W. R. Sistrom (W. R. Sistrom, J. Gen. Microbiol. 22:77-85, 1960) has been modified to allow the growth of
Rhodospirillum rubrum
in large-scale batch cultures under dark, semiaerobic conditions. The simultaneous use of two substrates, NH
4
-succinate (46 mM) and fructose (0.3%), which are utilized in aerobic and fermentative metabolism, respectively, leads to very high cell densities with a maximal yield of photosynthetic membranes.
Influence of Yucca shidigera extract on ruminal ammonia concentrations and ruminal microorganisms
Authors: Wallace R J , Arthaud L , Newbold C J
Published: January 2020

An extract of the desert plant Yucca shidigera was assessed for its possible benefit in ruminal fermentation. The extract bound ammonia in aqueous solution when concentrations of ammonia were low (up to 0.4 mM) and when the extract was added at a high concentration to the sample (20%, vol/vol). The apparent ammonia-binding capability was retained after autoclaving and was decreased slightly following dialysis. Acid-precipitated extract was inactive. No evidence of substantial ammonia binding was found at higher ammonia concentrations (up to 30 mM). When Y. shidigera extract (1%, vol/vol) was added to strained rumen fluid in vitro, a small (6%) but significant (P < 0.05) decrease in ammonia concentration occurred, apparently because of decreased proteolysis. Inclusion of Y. shidigera extract (1%, vol/vol) in the growth medium of the rumen bacterium Streptococcus bovis ES1 extended its lag phase, while growth of Butyrivibrio fibrisolvens SH13 was abolished. The growth of Prevotella (Bacteroides) ruminicola B(1)4 was stimulated, and that of Selenomonas ruminantium Z108 was unaffected. Protozoal activity, as measured by the breakdown of 14C-leucine-labelled S. ruminantium in rumen fluid incubated in vitro, was abolished by the addition of 1% extract. The antimicrobial activities were unaffected by precipitating tannins with polyvinylpyrrolidone, but a butanol extract, containing the saponin fraction, retained its antibacterial and antiprotozoal effects. Saponins from other sources were less effective against protozoa than Y. shidigera saponins. Y. shidigera extract, therefore, appears unlikely to influence ammonia concentration in the rumen directly, but its saponins have antimicrobial properties, particularly in suppressing ciliate protozoa, which may prove beneficial to ruminal fermentation and may lead indirectly to lower ruminal ammonia concentrations.
Cloning and DNA sequence of the gene coding for Bacillus stearothermophilus T-6 xylanase
Authors: Gat O , Lapidot A , Alchanati I , Regueros C , Shoham Y
Published: January 2020

Bacillus stearothermophilus T-6 produces an extracellular thermostable xylanase. Affinity-purified polyclonal serum raised against the enzyme was used to screen a genomic library of B. stearothermophilus T-6 constructed in lambda-EMBL3. Two positive phages were isolated, both containing similar 13-kb inserts, and their lysates exhibited xylanase activity. A 3,696-bp SalI-BamHI fragment containing the xylanase gene was subcloned in Escherichia coli and subsequently sequenced. The open reading frame of xylanase T-6 consists of 1,236 bp. On the basis of sequence similarity, two possible -10 and -35 regions, a ribosome-binding site at the 5' end of the gene and a potential transcriptional termination motif at the 3' end of the gene, were identified. From the previously known N-terminal amino acid sequence of xylanase T-6 and the possible ribosome-binding site, a putative 28-amino-acid signal peptide was deduced. The mature xylanase T-6 consists of 379 amino acids with a calculated molecular weight and pI of 43,808 and 6.88, respectively. Multiple alignment of beta-glycanase amino acid sequences revealed highly conserved regions. Northern (RNA) blot analysis indicated that the xylanase T-6 transcript is about 1.4 kb and that the induction of this enzyme synthesis by xylose is on the transcriptional level.
Transformations of Aromatic Compounds by
Nitrosomonas europaea
Authors: Keener William K. , Arp Daniel J.
Published: January 2020

Benzene and a variety of substituted benzenes inhibited ammonia oxidation by intact cells of
Nitrosomonas europaea.
In most cases, the inhibition was accompanied by transformation of the aromatic compound to a more oxidized product or products. All products detected were aromatic, and substituents were often oxidized but were not separated from the benzene ring. Most transformations were enhanced by (NH
4
)
2
SO
4
(12.5 mM) and were prevented by C
2
H
2
, a mechanism-based inactivator of ammonia monooxygenase (AMO). AMO catalyzed alkyl substituent hydroxylations, styrene epoxidation, ethylbenzene desaturation to styrene, and aniline oxidation to nitrobenzene (and unidentified products). Alkyl substituents were preferred oxidation sites, but the ring was also oxidized to produce phenolic compounds from benzene, ethylbenzene, halobenzenes, phenol, and nitrobenzene. No carboxylic acids were identified. Ethylbenzene was oxidized via styrene to two products common also to oxidation of styrene; production of styrene is suggestive of an electron transfer mechanism for AMO. Iodobenzene and 1,2-dichlorobenzene were oxidized slowly to halophenols; 1,4-dichlorobenzene was not transformed. No 2-halophenols were detected as products. Several hydroxymethyl (-CH
2
OH)-substituted aromatics and
p
-cresol were oxidized by C
2
H
2
-treated cells to the corresponding aldehydes, benzaldehyde was reduced to benzyl alcohol, and
o
-cresol and 2,5-dimethylphenol were not depleted.
Energy-spilling reactions of Streptococcus bovis and resistance of its membrane to proton conductance
Authors: Cook G M , Russell J B
Published: January 2020

Glucose-excess cultures of Streptococcus bovis consumed glucose faster than the amount that could be explained by growth or maintenance, and nongrowing chloramphenicol-treated cells had a rate of glucose consumption that was 10-fold greater than the maintenance rate. Because N,N-dicyclohexylcarbodiimide, an inhibitor of the membrane-bound F1F0 ATPase, eliminated the nongrowth energy dissipation (energy spilling) without a decrease in ATP and the rate of energy spilling could be increased by the protonophore 3,3',4',5-tetrachlorosalicylanilide, it appeared that a futile cycle of protons through the cell membrane was responsible for most of the energy spilling. When the rate of energy spilling was decreased gradually with iodoacetate, there was only a small decrease in the phosphorylation potential (delta G'p) and the theoretical estimate of H+ per ATP decreased from 4.2 to 3.6. On the bases of this ratio of H+ to ATP and the rate of ATP production, the flux of protons (amperage) across the cell membrane was directly proportional to the rate of energy spilling. Amperage values estimated from delta G'p were, however, nearly twice as great as values which were estimated from the heat production (delta H) of the cells [amperage = (0.38 x wattage)/delta p]. The last comparison indicated that only a fraction of the delta G of ATP hydrolysis was harvested by the F1F0 ATPase to pump protons. Both estimates of amperage indicated that the resistance of the cell membrane to proton conductance was inversely proportional to the log of the energy-spilling rate.
Lipid Peroxidation by the Manganese Peroxidase of
Phanerochaete chrysosporium
Is the Basis for Phenanthrene Oxidation by the Intact Fungus
Authors: Moen Mark A. , Hammel Kenneth E.
Published: January 2020

The manganese peroxidase (MnP) of
Phanerochaete chrysosporium
supported Mn(II)-dependent, H
2
O
2
-independent lipid peroxidation, as shown by two findings: linolenic acid was peroxidized to give products that reacted with thiobarbituric acid, and linoleic acid was peroxidized to give hexanal. MnP also supported the slow oxidation of phenanthrene to 2,2′-diphenic acid in a reaction that required Mn(II), oxygen, and unsaturated lipids. Phenanthrene oxidation to diphenic acid by intact cultures of
P. chrysosporium
occurred to the same extent that oxidation in vitro did and was stimulated by Mn. These results support a role for MnP-mediated lipid peroxidation in phenanthrene oxidation by
P. chrysosporium
.
Occurrence and distribution of Legionella species in composted plant materials
Authors: Hughes M S , Steele T W
Published: January 2020

Legionellae were found in many samples of composted plant matter obtained from home gardeners and from facilities which undertook bulk composting. The predominant species isolated from these composts was Legionella pneumophila, the strains of which belonged to serogroups other than serogroup 1. Other Legionella species were present in many samples. Legionella longbeachae serogroup 1, which is implicated in human infections in South Australia, was present in samples obtained from two of six facilities composting large volumes of material and from 3 of 30 gardeners. Many of the species or strains isolated from composts have not been implicated as causative agents of legionellosis in South Austrailia, but some cause infection in healthy and immunosuppressed persons.
Root-to-Root Travel of the Beneficial Bacterium
Azospirillum brasilense
Authors: Bashan Yoav , Holguin Gina
Published: January 2020

The root-to-root travel of the beneficial bacterium
Azospirillum brasilense
on wheat and soybean roots in agar, sand, and light-textured soil was monitored. We used a motile wild-type (Mot
+
) strain and a motility-deficient (Mot
-
) strain which was derived from the wild-type strain. The colonization levels of inoculated roots were similar for the two strains. Mot
+
cells moved from inoculated roots (either natural or artificial roots in agar, sand, or light-textured soil) to noninoculated roots, where they formed a band-type colonization composed of bacterial aggregates encircling a limited part of the root, regardless of the plant species. The Mot
-
strain did not move toward noninoculated roots of either plant species and usually stayed at the inoculation site and root tips. The effect of attractants and repellents was the primary factor governing the motility of Mot
+
cells in the presence of adequate water. We propose that interroot travel of
A. brasilense
is an essential preliminary step in the root-bacterium recognition mechanism. Bacterial motility might have a general role in getting
Azospirillum
cells to the site where firmer attachment favors colonization of the root system.
Azospirillum
travel toward plants is a nonspecific active process which is not directly dependent on nutrient deficiency but is a consequence of a nonspecific bacterial chemotaxis, influenced by the balance between attractants and possibly repellents leaked by the root.
Effect of relative humidity on fungal colonization of fiberglass insulation
Authors: Ezeonu I M , Noble J A , Simmons R B , Price D L , Crow S A , Ahearn D G
Published: January 2020

Fiberglass duct liners and fiberglass duct boards from eight buildings whose occupants complained of unacceptable or moldy odors in the air were found to be heavily colonized by fungi, particularly by Aspergillus versicolor. Unused fiberglass was found to be susceptible to fungal colonization in environmental chambers dependent upon relative humidity. No colonization was observed at relative humidities below 50%.
Buffering Capacity of Pigmented and Nonpigmented Strains of
Serratia marcescens
Authors: Rius Núria , Solé Montserrat , Francia Alicia , Lorén José G.
Published: January 2020

The pigmented strain
Serratia marcescens
ATCC 274 had a higher buffering capacity and a higher membrane H
+
conductance than
S. marcescens
GP, a spontaneous nonpigmented mutant of ATCC 274. The data suggest that mutations which apparently affect only the synthesis of a secondary metabolite can modify buffering capacity and passive H
+
conductance.
Detection, purification, and partial characterization of plantaricin C, a bacteriocin produced by a Lactobacillus plantarum strain of dairy origin
Authors: González B , Arca P , Mayo B , Suárez J E
Published: January 2020

A bacteriocin produced by Lactobacillus plantarum LL441 was selected from the inhibitory products of 75 mesophilic lactobacilli because of its potency and broad spectrum. It is a peptide of 3.5 kDa whose amino-terminal sequence is NH2-K-K-T-K-K-N-X-S-G-D-I-. It is bactericidal and, in some cases, bacteriolytic. The peptide, called plantaricin C, retained its activity after boiling, storage, and treatment at different pHs.
Bacillus DNA in fossil bees: an ancient symbiosis?
Authors: Cano R J , Borucki M K , Higby-Schweitzer M , Poinar H N , Poinar G O , Pollard K J
Published: January 2020

We report here the isolation of DNA from abdominal tissue of four extinct stingless bees (Proplebeia dominicana) in Dominican amber, PCR amplification of a 546-bp fragment of the 16S rRNA gene from Bacillus spp., and their corresponding nucleotide sequences. These sequences were used in basic local alignment search tool searches of nonredundant nucleic acid data bases, and the highest scores were obtained with 16S rRNA sequences from Bacillus spp. Phylogenetic inference analysis by the maximum-likelihood method revealed close phylogenetic relationships of the four presumed ancient Bacillus sequences with Bacillus pumilus, B. firmus, B. subtilis, and B. circulans. These four extant Bacillus spp. are commonly isolated from abdominal tissue of stingless bees. The close phylogenetic association of the extracted DNA sequences with these bee colonizers suggests that a similar bee-Bacillus association existed in the extinct species P. dominicana.
Isolation and Identification of Environmental Mycobacteria in the
Mycobacterium bovis
BCG Trial Area of South India
Authors: Kamala T. , Paramasivan C. N. , Herbert Daniel , Venkatesan P. , Prabhakar R.
Published: January 2020

The isolation profiles of environmental mycobacteria present in soil, water, and dust samples, and sputum samples of persons with symptoms of chest infection in the South Indian
Mycobacterium bovis
BCG (bacillus Calmette-Guérin) trial area were compared. Isolates belonging to the
Mycobacterium avium-intracellulare-scrofulaceum
complex were predominant in water, dust, and sputum samples and
Mycobacterium fortuitum
-complex organisms were predominant in soil samples irrespective of the season of the year.
Photometabolism of Heterocyclic Aromatic Compounds by
Rhodopseudomonas palustris
OU 11
Authors: Sasikala C. , Ramana C. V. , Rao P. Raghuveer
Published: January 2020

Rhodopseudomonas palustris
OU 11 (ATCC 51186; DSM 7375) isolated from a pond of chemical industry effluent could anaerobically photometabolize heterocyclic aromatic compounds belonging to the pyridine and pyrazine groups only after a period of adaptation on pyrazinoic acid of 5 to 6 weeks. Growth on heterocyclic compounds was light dependent. The effects of various concentrations of heterocyclic compounds on growth suggest that higher concentrations of these compounds inhibit growth and are toxic.
Anaerobic Degradation of Normal- and Branched-Chain Fatty Acids with Four or More Carbons to Methane by a Syntrophic Methanogenic Triculture
Authors: Wu Wei-Min , Jain Mahendra K. , Zeikus J. Gregory
Published: January 2020

Syntrophic degradation of normal- and branched-chain fatty acids with 4 to 9 carbons was investigated with a mesophilic syntrophic isobutyrate-butyrate-degrading triculture consisting of the non-spore-forming, syntrophic, fatty acid-degrading, gram-positive rod-shaped strain IB,
Methanobacterium formicicum
T1N, and
Methanosarcina mazei
T18. This triculture converted butyrate and isobutyrate to methane and converted valerate and 2-methylbutyrate to propionate and methane. This triculture also degraded caproate, 4-methylvalerate, heptanoate, 2-methylhexanoate, caprylate, and pelargoate. During the syntrophic conversion of isobutyrate and butyrate, a reversible isomerization between butyrate and isobutyrate occurred; isobutyrate and butyrate were isomerized to the other isomeric form to reach nearly equal concentrations and then their concentrations decreased at the same rates. Butyrate was an intermediate of syntrophic isobutyrate degradation. When butyrate was degraded in the presence of propionate, 2-methylbutyrate was synthesized from propionate and isobutyrate formed from butyrate. During the syntrophic degradation of valerate, isobutyrate, butyrate, and 2-methylbutyrate were formed and then degraded. During syntrophic degradation of 2-methylbutyrate, isobutyrate and butyrate were formed and then degraded.
Inoculum Density-Dependent Mortality and Colonization of the Phyllosphere by
Pseudomonas syringae
Authors: Wilson Mark , Lindow Steven E.
Published: January 2020

Pseudomonas syringae
inocula containing cell concentrations ranging from 10
5
to 10
9
cells per ml were applied to the primary leaves of bean plants. The plants were incubated under conditions of high temperature and illumination and low relative humidity. Bacterial mortality rates and the proportional population decline of the inoculum were lowest at the highest inoculum concentrations. Addition of a high concentration of heat-killed cells to the inoculum containing a low concentration of viable cells significantly reduced both the mortality rate and the proportional population decline of the viable cells. The mechanisms underlying this density-dependent mortality may include cooperative protective effects of extracellular factors, such as bacterial extracellular polysaccharides, and physical protection by neighboring cells. Although epiphytic populations derived from inoculum concentrations of 10
8
or 10
9
cells per ml tended toward 10
6
CFU/g, the presumed carrying capacity of the leaf, populations derived from lower inoculum concentrations never achieved this carrying capacity. Assuming that epiphytic populations of
P. syringae
reside in discrete protected sites, our results suggest that at low inoculum concentrations, following a period of environmental stress, the number of viable cells may have dropped to zero in some sites; hence, the carrying capacity of the leaf could not be achieved.
Degradation of alkylphenol ethoxylates by Pseudomonas sp. strain TR01
Authors: Maki H , Masuda N , Fujiwara Y , Ike M , Fujita M
Published: January 2020

An alkylphenol ethoxylate-degrading bacterium was isolated from activated sludge of a municipal sewage treatment plant by enrichment culture. This organism was found to belong to the genus Pseudomonas; since no corresponding species was identified, we designated it as Pseudomonas sp. strain TR01. This strain had an optimal temperature and pH of 30 degrees C and 7, respectively, for both growth and the degradation of Triton N-101 (a nonylphenol ethoxylate in which the average number of ethylene oxide [EO] units is 9.5). The strain was unable to mineralize Triton N-101 but was able to degrade its EO chain exclusively. The resulting dominant intermediate was identified by normal-phase high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry as a nonylphenol ethoxylate with 2 mol of EO units. A carboxylated metabolite, [(nonylphenoxy)ethoxy]acetic acid, was detected by gas chromatography-mass spectrometry. This bacterium also metabolized alcohol ethoxylates with various numbers of EO units but not polyethylene glycols whatever their degree of polymerization. By oxygen consumption assay, the alkyl group or arene corresponding to the hydrophobic part of alcohol ethoxylates or alkylphenol ethoxylates was shown to contribute to the induction of the metabolic system of the EO chain of Triton N-101, instead of the EO chain itself, which corresponds to its hydrophilic part. Thus, the isolated pseudomonad bacterium has unique substrate assimilability: it metabolizes the EO chain only when the chain linked to bulky hydrophobic groups.
Effect of distance from the polluting focus on relative concentrations of Bacteroides fragilis phages and coliphages in mussels
Authors: Lucena F , Lasobras J , McIntosh D , Forcadell M , Jofre J
Published: January 2020

Concentrations of fecal bacteria, somatic and F-specific coliphages, and phages infecting Bacteroides fragilis in naturally occurring black mussels (Mytilus edulis) were determined. Mussels were collected over a 7-month period at four sampling sites with different levels of fecal pollution. Concentrations of both fecal bacteria and bacteriophages in mussel meat paralleled the concentration of fecal bacteria in the overlying waters. Mussels bioaccumulated efficiently, although with different efficiencies, all of the microorganisms studied. Ratios comparing the levels of microorganisms in mussels were determined. These ratios changed in mussels collected at the different sites. They suggest that bacteriophages infecting B. fragilis and somatic coliphages have the lowest decay rates among the microorganisms studied, with the exception of Clostridium perfringens. On the contrary, concentrations of F-specific coliphages showed a greater rate of decay than the other bacteriophages at sites more distant from the focus of contamination. Additionally, levels of enteroviruses were studied in a number of samples, and in these samples, the B. fragilis bacteriophages clearly outnumbered the enteroviruses. The results of this study indicate that, under the environmental conditions studied, the fate of phages infecting B. fragilis released into the marine environment resembles that of human viruses more than any other microorganism examined.
Characterization of metal-binding bioflocculants produced by the cyanobacterial component of mixed microbial mats
Authors: Bender J , Rodriguez-Eaton S , Ekanemesang U M , Phillips P
Published: January 2020

Mixed-species microbial mats that were dominated by the cyanobacterium Oscillatoria sp. and contained heterotrophic and purple autotrophic bacteria were constructed for specific bioremediation applications. When the mats were challenged with metals, production and secretion of metal-binding extracellular polysaccharide bioflocculants were observed. The concentration of these negatively charged polysaccharides was correlated with the removal of manganese from the water column beneath a surface microbial mat. Bioflocculants from an Oscillatoria sp. that was isolated from the mat were collected and concentrated for characterization. A chromatographic analysis revealed a heterogeneous population of polysaccharides with respect to charge density and molecular size. The subpopulation of polysaccharides which exhibited the highest level of flocculating activity was polyanionic and had a molecular weight of more than 200,000. A glycosyl analysis of the bioflocculants revealed the presence of galacturonic acid (2.2%) and glucuronic acid (1.86%). The presence of these components, which were negatively charged at the pH levels generated by the mats during photosynthesis (pH > 7.5), may account for the metal-binding properties of the mats.
Role of alginate lyase in cell detachment of Pseudomonas aeruginosa
Authors: Boyd A , Chakrabarty A M
Published: January 2020

The exopolysaccharide alginate of Pseudomonas aeruginosa was shown to be important in determining the degree of cell detachment from an agar surface. Nonmucoid strain 8822 gave rise to 50-fold more sloughed cells than mucoid strains 8821 and 8830. Alginate anchors the bacteria to the agar surface, thereby influencing the extent of detachment. The role of the P. aeruginosa alginate lyase in the process of cell sloughing was investigated. Increased expression of the alginate lyase in mucoid strain 8830 led to alginate degradation and increased cell detachment. Similar effects were seen both when the alginate lyase was induced at the initial stage of cell inoculation and when it was induced at a later stage of growth. It appears that high-molecular-weight alginate polymers are required to efficiently retain the bacteria within the growth film. When expressed from a regulated promoter, the alginate lyase can induce enhanced sloughing of cells because of degradation of the alginate. This suggests a possible role for the lyase in the development of bacterial growth films.
Inheritance of Strain Instability (Sectoring) in the Commercial Button Mushroom,
Agaricus bisporus
Authors: Li Aimin , Begin Marc , Kokurewicz Karl , Bowden Christine , Horgen Paul A.
Published: January 2020

The button mushroom,
Agaricus bisporus
, is a commercially important cultivated filamentous fungus. During the last decade, the button mushroom industry has depended mainly on two strains (or derivatives of these two strains). Using one of these highly successful strains (strain U1) we examined the phenomenon of strain instability, specifically, the production of irreversible sectors. Three “stromatal” and three “fluffy” sectors were compared with a healthy type U1 strain and with a wild-collected isolate. Compost colonization and fruit body morphology were examined. The main objective of this study, however, was to examine the meiotic stability of the sectored phenotype. Single basidiospores were isolated and subjected to a grain bioassay in which the ability to produce sectors was measured. Our results were as follows: (i) basidiospore cultures obtained from a wild-collected isolate showed no tendency to produce sectors; (ii) approximately 5% of the basidiospore cultures obtained from healthy type U1 strains produced irreversible sectors in the grain bioassay; (iii) the five primary sectors examined produced basidiospore cultures, half of which produced normal-looking growth in the grain bioassay and half of which produced some degree of sectoring; and (iv) the one sectored isolate that represented the F2 generation gave ratios similar to the 1:1 ratio observed for the F1 cultures.
Novel Processes for Anaerobic Sulfate Production from Elemental Sulfur by Sulfate-Reducing Bacteria
Authors: Lovley Derek R. , Phillips Elizabeth J. P.
Published: January 2020

Sulfate reducers and related organisms which had previously been found to reduce Fe(III) with H
2
or organic electron donors oxidized S
0
to sulfate when Mn(IV) was provided as an electron acceptor. Organisms catalyzing this reaction in washed cell suspensions included
Desulfovibrio desulfuricans, Desulfomicrobium baculatum, Desulfobacterium autotrophicum, Desulfuromonas acetoxidans
, and
Geobacter metallireducens
. These organisms produced little or no sulfate from S
0
with Fe(III) as a potential electron acceptor or in the absence of an electron acceptor. In detailed studies with
Desulfovibrio desulfuricans
, the stoichiometry of sulfate and Mn(II) production was consistent with the reaction S
0
+ 3 MnO
2
+ 4H
+
→SO
4
2-
+ 3Mn(II) + 2H
2
O. None of the organisms evaluated could be grown with S
0
as the sole electron donor and Mn(IV) as the electron acceptor. In contrast to the other sulfate reducers evaluated,
Desulfobulbus propionicus
produced sulfate from S
0
in the absence of an electron acceptor and Fe(III) oxide stimulated sulfate production. Sulfide also accumulated in the absence of Mn(IV) or Fe(III). The stoichiometry of sulfate and sulfide production indicated that
Desulfobulbus propionicus
disproportionates S
0
as follows: 4S
0
+ 4H
2
O→SO
4
2-
+ 3HS
-
+ 5 H
+
. Growth of
Desulfobulbus propionicus
with S
0
as the electron donor and Fe(III) as a sulfide sink and/or electron acceptor was very slow. The S
0
oxidation coupled to Mn(IV) reduction described here provides a potential explanation for the Mn(IV)-dependent sulfate production that previous studies have observed in anoxic marine sediments.
Desulfobulbus propionicus
is the first example of a pure culture known to disproportionate S
0
.
Molecular characterization of aflR, a regulatory locus for aflatoxin biosynthesis
Authors: Woloshuk C P , Foutz K R , Brewer J F , Bhatnagar D , Cleveland T E , Payne G A
Published: January 2020

Aflatoxins belong to a family of decaketides that are produced as secondary metabolites by Aspergillus flavus and A. parasiticus. The aflatoxin biosynthetic pathway involves several enzymatic steps that appear to be regulated by the afl2 gene in A. flavus and the apa2 gene in A. parasiticus. Several lines of evidence indicate that these two genes are homologous. The DNA sequences of the two genes are highly similar, they both are involved in the regulation of aflatoxin biosynthesis, and apa2 can complement the afl2 mutation in A. flavus. Because of these similarities, we propose that these two genes are homologs, and because of the ability of these genes to regulate aflatoxin biosynthesis, we suggest that they be designated aflR. We report here the further characterization of aflR from A. flavus and show that aflR codes for a 2,078-bp transcript with an open reading frame of 1,311 nucleotides that codes for 437 amino acids and a putative protein of 46,679 daltons. Analysis of the predicted amino acid sequence indicated that the polypeptide contains a zinc cluster motif between amino acid positions 29 and 56. This region contains the consensus sequence Cys-Xaa2-Cys-Xaa6-Cys-Xaa6-Cys-Xaa2-Cys-Xaa6+ ++-Cys. This motif has been found in several fungal transcriptional regulatory proteins. DNA hybridization of the aflR gene with genomic digests of seven polyketide-producing fungi revealed similar sequences in three other species related to A. flavus: A. parasiticus, A. oryzae, and A. sojae. Finally, we present evidence for an antisense transcript (aflRas) derived from the opposite strand of aflR, suggesting that the aflR locus involves some form of antisense regulation.
Effects of Sieving, Storage, and Incubation Temperature on the Phospholipid Fatty Acid Profile of a Soil Microbial Community
Authors: Petersen Søren O. , Klug Michael J.
Published: January 2020

Disturbances typically associated with the study of soil microbial communities, i.e., sieving, storage, and subsequent incubation at elevated temperatures, were investigated with phospholipid fatty acid (PLFA) analyses. Treatment effects were quantified by statistical analyses of the mole percentage distribution of the individual fatty acids. Changes in the concentrations of individual fatty acids over a 7-week storage period at 4.5°C were generally not statistically significant. Sieving effects (mesh size, 4 or 2 mm) on CO
2
evolution and the PLFA profile were monitored over 3 weeks; the physical disturbance had only minor effects, although some damage to fungal hyphae by the first sieving (<4 mm) was suggested by a decrease in the signature fatty acid 18:2 ω6
c
. Temperature effects were investigated by incubating soil for up to 3 weeks at 4.5, 10, or 25°C. Principal component analyses demonstrated a significant shift in the PLFA composition at 25°C over the first 2 weeks, while changes at the other two temperatures were minor. Several of the changes observed at 25°C could be explained with reference to mechanisms of temperature adaptation or as a response to conditions of stress, including a decrease in the degree of unsaturation, an increased production of cyclopropyl fatty acids, and increased ratios of the branched-chain fatty acids
iso
-15:0 and
iso
-17:0 over
anteiso
-15:0 and
anteiso
-17:0, respectively. A decrease in the total amount of PLFA was also indicated.
Trichloroethylene and chloroform degradation by a recombinant pseudomonad expressing soluble methane monooxygenase from Methylosinus trichosporium OB3b
Authors: Jahng D , Wood T K
Published: January 2020

Soluble methane monooxygenase (sMMO) from Methylosinus trichosporium OB3b can degrade many halogenated aliphatic compounds that are found in contaminated soil and groundwater. This enzyme oxidizes the most frequently detected pollutant, trichloroethylene (TCE), at least 50 times faster than other enzymes. However, slow growth of the strain, strong competition between TCE and methane for sMMO, and repression of the smmo locus by low concentrations of copper ions limit the use of this bacterium. To overcome these obstacles, the 5.5-kb smmo locus of M. trichosporium OB3b was cloned into a wide-host-range vector (to form pSMMO20), and this plasmid was electroporated into five Pseudomonas strains. The best TCE degradation results were obtained with Pseudomonas putida F1/pSMMO20. The plasmid was maintained stably, and all five of the sMMO proteins (alpha, beta, and gamma hydroxylase proteins, reductase, and component B) were observed clearly by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western immunoblotting. TCE degradation rates were quantified for P. putida F1/pSMMO20 with a gas chromatograph (Vmax = 5 nmol per min per mg of protein), and the recombinant strain mineralized 55% of the TCE (10 microM) as indicated by measuring chloride ion concentrations with a chloride ion-specific electrode. The maximum TCE degradation rate obtained with the recombinant strain was lower than that of M. trichosporium OB3b but greater than other TCE-degrading recombinants and most well-studied pseudomonads. In addition, this recombinant strain mineralizes chloroform (a specific substrate for sMMO), grows much faster than M. trichosporium OB3b, and degrades TCE without competitive inhibition from the growth substrate.
Oxidative Bioconversion of Cholesterol by
Pseudomonas
sp. Strain ST-200 in a Water-Organic Solvent Two-Phase System
Authors: Aono Rikizo , Doukyu Noriyuki , Kobayashi Hideki , Nakajima Harushi , Horikoshi Koki
Published: January 2020

Pseudomonas
sp. strain ST-200, which is capable of conversion of cholesterol, was isolated from humus soil. This organism effectively modified cholesterol dissolved in an organic solvent by dehydrogenation and oxygenation. When the organism was grown in a medium overlaid with a 10% volume of a mixed organic solvent (
p
-xylene and diphenylmethane; 3:7, vol/vol) containing cholesterol (20 mg/ml), the cholesterol concentration in the organic solvent was reduced to only 0.4 mg/ml after 8 days. Although the organism did not assimilate cholesterol, 98% of the cholesterol initially present disappeared. The organic solvent layer contained two major and three minor compounds converted from cholesterol. The major compounds were 6β-hydroxycholest-4-en-3-one (8.9 mg/ml) and cholest-4-ene-3,6-dione (7.6 mg/ml). The concentrations of these compounds were equivalent to 43 and 37% of the cholesterol initially present. This organism would provide an effective and convenient system to oxidize the C-3 and -6 positions of cholesterol by introduction of a hydroxyl or ketone group.
International dissemination of epidemic Vibrio cholerae by cargo ship ballast and other nonpotable waters
Authors: McCarthy S A , Khambaty F M
Published: January 2020

In 1991 and 1992, toxigenic Vibrio cholerae O1, serotype Inaba, biotype El Tor, was recovered from nonpotable (ballast, bilge, and sewage) water from five cargo ships docked in ports of the U.S. Gulf of Mexico. Four of these ships had taken on ballast water in cholera-infected countries; the fifth took on ballast in a noninfected country. Isolates examined by pulsed-field gel electrophoresis were indistinguishable from the Latin American epidemic strain, C6707; however, they differed significantly from the endemic Gulf Coast strain (VRL 1984), the sixth-pandemic strain (569-B), and a V. cholerae non-O1 strain isolated from a ship arriving from a foreign port. On the basis of our findings, the Food and Drug Administration recommended that the U.S. Coast Guard issue an advisory to shipping agents and captains requesting that ballast waters be exchanged on the high seas before entry of ships into U.S. ports.