bluuebunny/crossref_metadata_2025 huggingface dataset:
Queen recruitment and split sex ratios in polygynous colonies of the ant Formica exsecta
Authors: Brown William D. , Keller Laurent
Published: March 2003

Sex ratios in social insects have become a general model for tests of inclusive fitness theory, sex ratio theory and parent–offspring conflict. In populations of Formica exsecta with multiple queens per colony, sex ratios vary greatly among colonies and the dry‐weight sex ratio is extremely male‐biased, with 89% of the colonies producing males but no gynes (reproductive females). Here we test the queen‐replenishment hypothesis, which was proposed to explain sex ratio specialization in this and other highly polygynous ants (i.e. those with many queens per nest). This hypothesis proposes that, in such ants, colonies produce gynes to recruit them back into the colony when the number of resident queens falls below a given threshold limiting colony productivity or survival. We tested predictions of the queen‐replenishment hypothesis by following F. exsecta colonies across two breeding seasons and relating the change in effective queen number with changes in sex ratio, colony size and brood production. As predicted by the queen‐replenishment hypothesis, we found that colonies that specialized in producing females increased their effective queen number and were significantly more likely to specialize in male production the following year. The switch to male production also coincided with a drop in productivity per queen as predicted. However, adoption of new queens did not result in a significant increase in total colony productivity the following year. We suggest that this is because queen production comes at the expense of worker production and thus queen production leads to resource limitation the following year, buffering the effect of greater queen number on total productivity.
Oviposition preferences of herbivores are affected by tritrophic interaction webs
Authors: Shiojiri Kaori , Takabayashi Junji , Yano Shuichi , Takafuji Akio
Published: March 2003

Two tritrophic systems were experimentally coupled in the present study. One system consisted of a cabbage plant (Brassica oleracea), diamondback moth larvae (Plutella xylostella) and their parasitic wasp (Cotesia plutellae). The other system consisted of a cabbage plant, cabbage butterfly (Pieris rapae) larvae and their parasitic wasp (Cotesia glomerata). First, we demonstrated that parasitism by C. glomerata and C. plutellae increased and decreased, respectively, on plants infested by both herbivore species than on plants infested by their host larvae alone. We then demonstrated that adult Pl. xylostella oviposited preferentially on plants infested with Pi. rapae, whereas adult Pi. rapae revealed no significant preferences between uninfested plants or plants infested with Pl. xylostella. Based on the present results and those of our previous study, we discuss the oviposition preferences of herbivores in tritrophic contexts.
Herbivorous animals can mitigate unfavourable ratios of energy and material supplies by enhancing nutrient recycling
Authors: Urabe Jotaro , Elser James J. , Kyle Marcia , Yoshida Takehito , Sekino Tatsuki , Kawabata Zenichiro
Published: March 2003

Recent evidence shows that high supply ratios of light and nutrients limit planktonic herbivore growth by lowering the nutritional quality of algae. Over longer time scales, however, grazers may ameliorate this effect by their impact on nutrient cycling. We examine this possibility using two species of the herbivorous zooplankter Daphnia and its algal prey under different light intensities and low phosphorus supply in laboratory microcosms. At high light, Daphnia biomass was limited for a substantial period because of low P content of algal cells. However, a gradual increase in Daphnia density eventually improved food quality through grazing and nutrient cycling and via a novel process involving positive density dependence. Competitive exclusion of one of the two Daphnia species occurred under low light but not under high light when algae were nutritionally unsuitable. Such stoichiometrically mediated interactions among herbivorous animals may represent important mechanisms that affect community structure and material flows in ecosystems.
Invasion success: does size really matter?
Authors: Miller A. W. , Hewitt C. L. , Ruiz G. M.
Published: March 2003

The recent paper by Roy et al. (2001) presents a compelling relationship between range limit shifts, climatic fluctuations, and body size for marine bivalves in the fossil record. However, their extension of body size as a correlate for contemporary marine bivalve introductions is problematic and requires further scrutiny. Unlike their analysis of the fossil assemblage, the approach used for contemporary invasions does not adequately control for dispersal mechanism (vector) or source region. First, their analysis included mariculture species, intentionally introduced because of their large size, creating a vector‐specific bias. Second, successful invaders from multiple source regions (Northern Hemisphere) were compared with potential invaders from a single source region (north‐eastern Pacific), leaving both source and vector as uncontrolled variables. We present an analysis of body size for bivalve introductions from a single vector and source region, indicating no correlation between body size and invasion success when eliminating intentional introduction, source region and transport vector as confounding factors.
Competition and character displacement in two species of scincid lizards
Authors: Melville Jane
Published: March 2003

The role of competition in habitat occupation and character displacement is investigated in two species of alpine lizards (Niveoscincus microlepidotus and N. greeni), using both controlled competition experiments and field‐based ecological work. Competition experiments demonstrate that interspecific aggression occurs between these closely related species, with the larger and more aggressive N. greeni being socially dominant. When these species occur in sympatry, N. microlepidotus was found to shift its habitat occupation to the heathlands, which provide less thermal opportunities. In addition, a reduction in body size occurred in both adult and neonatal N. microlepidotus at sympatric field sites. Differences in body size between N. microlepidotus and N. greeni in sympatry were significantly greater than in allopatry, indicating that character displacement is occurring. Results, combined with previous molecular and biogeographical data, suggest that there is a trend towards a reduction in body size and a restriction in habitat occupation in N. microlepidotus in the north‐east periphery of its distribution, which is shaped by competition with N. greeni.
Resource quantity, not resource heterogeneity, maintains plant diversity
Authors: Stevens M. Henry H. , Carson Walter P.
Published: March 2003

Resource heterogeneity has often been proposed to explain the maintenance of plant species diversity and patterns of species diversity along productivity gradients. Resource heterogeneity should maintain biodiversity by preventing competitive exclusion because different species are superior competitors in different parts of a heterogeneous environment. In natural systems, however, resource heterogeneity covaries with average resource supply rate, making the effect of heterogeneity difficult to isolate. Using a novel experimental approach, we tested the independent effects of resource heterogeneity and average supply rate on plant species diversity. We show that the average supply rate of the most limiting resource controlled species diversity, whereas heterogeneity of this resource had virtually no effect. These findings also suggest that biodiversity declines with increasing productivity because at high enough levels of productivity one resource may always be driven to sufficiently short supply to exclude many species.
Simple temporal models for ecological systems with complex spatial patterns
Authors: Pascual Mercedes , Roy Manojit , Franc Alain
Published: March 2003

Spatial patterns are ubiquitous in nature. Because these patterns modify the temporal dynamics and stability properties of population densities at a range of spatial scales, their effects must be incorporated in temporal ecological models that do not represent space explicitly. We demonstrate a connection between a simple parameterization of spatial effects and the geometry of clusters in an individual‐based predator–prey model that is both nonlinear and stochastic. Specifically we show that clusters exhibit a power‐law scaling of perimeter to area with an exponent close to unity. In systems with a high degree of patchiness, similar power‐law scalings can provide a basis for applying simple temporal models that assume well‐mixed conditions.
Overyielding in grassland communities: testing the sampling effect hypothesis with replicated biodiversity experiments
Authors: Hector Andy , Bazeley‐White Ellen , Loreau Michel , Otway Stuart , Schmid Bernhard
Published: March 2003

We derive and test some assumptions and predictions of the Sampling Effect Hypothesis (SEH) by examining the relationship between the traits of species in monoculture and their relative abundance in mixture, and by comparing polyculture performance with single‐species plots. Although we found a positive relationship between production in monoculture and dominance in mixtures as predicted by the SEH, the relationship had low explanatory power. Counter to predictions, the species with the highest monoculture biomass were not able to strongly dominate all mixtures; instead the dominance of these species decreased with increasing species richness. On average, polycultures did not achieve greater biomass than (transgressively overyield) the species in each mixture, or at each site, that was most productive in monoculture. However, mixture yields did transgressively overyield both the monoculture biomass of the dominant species in the mixtures, and the weighted average of all monocultures (non‐transgressive overyielding), both of which were positively related to increasing species richness. The varying responses of different overyielding tests resulted because resource partitioning and positive interactions were often counter‐balanced by selection for species with lower biomass than the highest‐yielding monocultures. Judging whether or not mixtures overyield therefore depends in part upon which species is the basis for comparison. We present a new general framework for overyielding analysis where every monoculture provides a potential comparison and from which the most relevant tests can be selected.
Virulence evolution via host exploitation and toxin production in spore‐producing pathogens
Authors: Day Troy
Published: March 2003

Many pathogens produce resilient free‐living propagules that allow their dissemination in the absence of direct contact between susceptible and infected hosts. One might expect pathogens capable of producing such long‐lived propagules to evolve high levels of virulence because their reproductive success is de‐coupled from the survival of their host. Despite some comparative data supporting this prediction, theory has questioned its general validity. I present theoretical results that incorporate two transmission routes neglected by previous theory: death‐mediated propagule production and direct host‐host transmission. This theory predicts that spore‐producing pathogens should evolve high levels of virulence under quite broad conditions. Moreover, a novel prediction of this theory is that the production of propagules can generate selection for the evolution of pathogen characteristics such as toxins whose sole function is to kill the host. This latter result reveals an unanticipated mechanism through which virulence is expected to evolve in spore‐producing pathogens.
Invasion theory and biological control
Authors: Fagan William F. , Lewis Mark A. , Neubert Michael G. , Van Den Driessche P.
Published: March 2003

Recent advances in the mathematical theory of invasion dynamics have much to offer to biological control. Here we synthesize several results concerning the spatiotemporal dynamics that occur when a biocontrol agent spreads into a population of an invading pest species. We outline conditions under which specialist and generalist predators can influence the density and rate of spatial spread of the pest, including the rather stringent conditions under which a specialist predator can successfully reverse a pest invasion. We next discuss the connections between long distance dispersal and invasive spread, emphasizing the different consequences of fast spreading pests and predators. Recent theory has considered the effects of population stage‐structure on invasion dynamics, and we discuss how population demography affects the biological control of invading pests. Because low population densities generally characterize early stages of an invasion, we discuss the lessons invasion theory teaches concerning the detectability of invasions. Stochasticity and density‐dependent dynamics are common features of many real invasions, influencing both the spatial character (e.g. patchiness) of pest invasions and the success of biocontrol agents. We conclude by outlining theoretical results delineating how stochastic effects and complex dynamics generated by density dependence can facilitate or impede biological pest control.
The mechanism of killing and exiting the protozoan host Acanthamoeba polyphaga by Legionella pneumophila
Authors: Gao Lian‐Yong , Abu Kwaik Yousef
Published: March 2003

The ability of Legionella pneumophila to cause legionnaires' disease is dependent on its capacity to replicate within cells in the alveolar spaces. The bacteria kill mammalian cells in two phases: induction of apoptosis during the early stages of infection, followed by an independent and rapid necrosis during later stages of the infection, mediated by a pore‐forming activity. In the environment, L. pneumophila is a parasite of protozoa. The molecular mechanisms by which L. pneumophila kills the protozoan cells, after their exploitation for intracellular proliferation, are not known. In an effort to decipher these mechanisms, we have examined induction of both apoptosis and necrosis in the protozoan Acanthamoeba polyphaga upon infection by L. pneumophila. Our data show that, although A. polyphaga undergoes apoptosis following treatment with actinomycin D, L. pneumophila does not induce apoptosis in these cells. Instead, intracellular L. pneumophila induces necrotic death in A. polyphaga, which is mediated by the pore‐forming activity. Mutants of L. pneumophila defective in expression of the pore‐forming activity are indistinguishable from the parental strain in intracellular replication within A. polyphaga. The parental strain bacteria cause necrosis‐mediated lysis of all the A. polyphaga cells within 48 h after infection, and all the intracellular bacteria are released into the tissue culture medium. In contrast, all cells infected by the mutants remain intact, and the intracellular bacteria are ‘trapped’ within A. polyphaga after the termination of intracellular replication. Failure to exit the host cell after termination of intracellular replication results in a gradual decline in the viability of the mutant strain bacteria within A. polyphaga starting 48 h after infection. Our data show that the pore‐forming activity of L. pneumophila is not required for intracellular bacterial replication within A. polyphaga but is required for killing and exiting the protozoan host upon termination of intracellular replication.
Field‐scale remediation of atrazine‐contaminated soil using recombinant Escherichia coli expressing atrazine chlorohydrolase
Authors: Strong Lisa C. , McTavish Hugh , Sadowsky Michael J. , Wackett Lawrence P.
Published: March 2003

We performed the first field‐scale atrazine remediation study in the United States using chemically killed, recombinant organisms. This field study compared biostimulation methods for enhancing atrazine degradation with a novel bioaugmentation protocol using a killed and stabilized whole‐cell suspension of recombinant Escherichia coli engineered to overproduce atrazine chlorohyrolase, AtzA. AtzA dechlorinates atrazine, producing non‐toxic and non‐phytotoxic hydroxyatrazine. Soil contaminated by an accidental spill of atrazine (up to 29 000 p.p.m.) supported significant populations of indigenous microorganisms capable of atrazine catabolism. Laboratory experiments indicated that supplementing soil with carbon inhibited atrazine biodegradation, but inorganic phosphate stimulated atrazine biodegradation. A subsequent field‐scale study consisting of nine (0.75 m3) treatment plots was designed to test four treatment protocols in triplicate. Control plots contained moistened soil; biostimulation plots received 300 p.p.m. phosphate; bioaugmentation plots received 0.5% (w/w) killed, recombinant E. coli cells encapsulating AtzA; and combination plots received phosphate plus the enzyme‐containing cells. After 8 weeks, atrazine levels declined 52% in plots containing killed recombinant E. coli cells, and 77% in combination plots. In contrast, atrazine levels in control and biostimulation plots did not decline significantly. These data indicate that genetically engineered bacteria overexpressing catabolic genes significantly increased degradation in this soil heavily contaminated with atrazine.
The biogeochemical controls of N2O production and emission in landfill cover soils: the role of methanotrophs in the nitrogen cycle
Authors: Mandernack Kevin W. , Kinney Chad A. , Coleman Dennis , Huang Yong‐Song , Freeman Katherine H. , Bogner Jean
Published: March 2003

Emissions of N2O from cover soils of both abandoned (> 30 years) and active landfills greatly exceed the maximum fluxes previously reported for tropical soils, suggesting high microbial activities for N2O production. Low soil matrix potentials (< −0.7 MPa) indicate that nitrification was the most likely mechanism of N2O formation during most of the time of sampling. Soil moisture had a strong influence on N2O emissions. The production of N2O was stimulated by as much as 20 times during laboratory incubations, when moisture was increased from −2.0 MPa to −0.6 MPa. Additional evidence from incubation experiments and δ13C analyses of fatty acids (18:1) diagnostic of methanotrophs suggests that N2O is formed in these soils by nitrification via methanotrophic bacteria. In a NH3(g)‐amended landfill soil, the rate of N2O production was significantly increased when incubated with 100 ppmv methane compared with 1.8 ppmv (atmospheric) methane. Preincubation of a landfill soil with 1% CH4 for 2 weeks resulted in higher rates of N2O production when subsequently amended with NH3(g) relative to a control soil preincubated without CH4. At one location, at the soil depth (9–16 cm) of maximum methane consumption and N2O production, we observe elevated concentrations of organic carbon and nitrogen and distinct minima in δ15N (+1.0‰) and δ13C (−33.8‰) values for organic nitrogen and organic carbon respectively. A δ13C value of −39.3‰ was measured for 18:1 carbon fatty acids in this soil, diagnostic of type II methanotrophs. The low δ15N value for organic nitrogen is consistent with N2 fixation by type II methanotrophs. These observations all point to a methanotrophic origin for the organic matter at this depth. The results of this study corroborate previous reports of methanotrophic nitrification and N2O formation in aqueous and soil environments and suggest a predominance of type II rather than type I or type X methanotrophs in this landfill soil.
Detection of abundant sulphate‐reducing bacteria in marine oxic sediment layers by a combined cultivation and molecular approach
Authors: Wieringa Elze B. A. , Overmann Jörg , Cypionka Heribert
Published: March 2003

The depth distribution and diversity of sulphate‐reducing bacteria (SRB) was analysed in the upper intertidal zone of a sandy marine sediment of the Dutch island Schiermonnikoog. The upper centimetre of the sediment included the oxic–anoxic interface and was cut into five slices. With each slice, most probable number (MPN) dilution series were set up in microtitre plates using five different substrates. In the deeper sediment layers, up to 1 × 108 cm−3 lactate‐utilizing SRB were counted, corresponding to 23% of the total bacterial count. From the highest positive dilutions of the MPN series, 27 strains of SRB were isolated in pure culture. Sequencing of a 580 bp fragment of the 16S rDNA revealed that 21 isolates had identical sequences, also identical with that of the previously described species Desulfomicrobium apsheronum. However, the diversity of the isolates was higher with respect to their physiological properties: a total of 11 different phenotypes could be distinguished. Genomic fingerprinting by enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction (PCR) revealed an even higher diversity of 22 different genotypes. A culture‐independent analysis by PCR and denaturing‐gradient gel electrophoresis (DGGE) revealed that the partial 16S rDNA sequence of the isolated D. apsheronum strains constituted a significant fraction of the Desulfovibrionaceae. The high subspecies diversity suggests that this abundant aggregate‐forming species may have evolved adaptations to different ecological niches in the oxic sediment layers.
Monitoring of Desulfitobacterium frappieri PCP‐1 in pentachlorophenol‐degrading anaerobic soil slurry reactors
Authors: Lanthier M. , Villemur R. , Lépine F. , Bisaillon J.‐G. , Beaudet R.
Published: March 2003

Anaerobic biodegradation of pentachlorophenol (PCP) was studied in rotative bioreactors containing 200 g of PCP‐contaminated soil and 250 ml of liquid medium. Reactors were bioaugmented with cells of Desulfitobacterium frappieri strain PCP‐1, a bacterium able to dehalogenate PCP to 3‐chlorophenol. Cells of strain PCP‐1 were detected by quantitative PCR for at least 21 days in reactors containing 500 mg of PCP per kg of soil but disappeared after 21 days in reactors with 750 mg of PCP per kg of soil. Generally, PCP was completely removed in less than 9 days in soils contaminated with 189 mg of PCP per kg of soil. Sorption of PCP to soil organic matter reduced its toxicity and enhanced the survival of strain PCP‐1. In some non‐inoculated reactors, the indigenous microorganisms of some soils were also able to degrade PCP. These results suggest that anaerobic dechlorination of PCP in soils by indigenous PCP‐degrading bacteria, or after augmentation with D. frappieri PCP‐1, should be possible in situ and ex situ when the conditions are favourable for the survival of the degrading microorganisms.
Bacterially mediated precipitation in marine stromatolites
Authors: Paerl Hans W. , Steppe Timothy F. , Reid R. Pamela
Published: March 2003

Stromatolites are laminated, lithified (CaCO3) sedimentary deposits formed by precipitation and/or sediment accretion by cyanobacterial–bacterial mat communities. Stromatolites have been associated with these communities as far back as the Precambrian era some 2+ billion years ago. The means by which microbial communities mediate the precipitation processes have remained unclear, and are the subject of considerable debate and speculation. Two alternative explanations for microbially mediated precipitation include: (i) cyanobacterial photosynthesis increases pH in a system supersaturated in respect of CaCO3, resulting in CaCO3 precipitation and then laminated lithification, and (ii) decomposition of cyanobacterial extracellular organic matter (e.g. sheaths, mucilage and organic acids) by microheterotrophs leads to release of organic‐bound Ca2+ ions and CaCO3 precipitation. We evaluated these explanations by examining metabolically active, lithifying stromatolitic mat communities from Highborne Cay, Bahamas, using microautoradiography. Microautoradiographic detection of 14CO2 fixation and 3H organic matter (

d‐glucose and an amino acid mixture) utilization by photosynthetically active cyanobacteria and microheterotrophs, combined with community‐level uptake experiments, indicate that bacteria, rather than cyanobacteria are the dominant sites of CaCO3 deposition. In the oligotrophic waters in which stromatolites exist, microheterotrophs are reliant on the photosynthetic community as a main source of organic matter. Therefore, autotrophic production indirectly controls microbially mediated precipitation and stromatolite formation in these shallow marine environments.
Thermophilic methanogens in rice field soil
Authors: Fey Axel , Chin Kuk Jeong , Conrad Ralf
Published: March 2003

The soil temperature in flooded Italian rice fields is generally lower than 30°C. However, two temperature optima at ≈ 41°C and 50°C were found when soil slurries were anoxically incubated at a temperature range of 10–80°C. The second temperature optimum indicates the presence of thermophilic methanogens in the rice field soil. Experiments with 14C‐labelled bicarbonate showed that the thermophilic CH4 was exclusively produced from H2/CO2. Terminal restriction fragment length polymorphism (T‐RFLP) of archaeal SSU rRNA gene fragments revealed a dramatic change in the archaeal community structure at temperatures > 37°C, with the euryarchaeotal rice cluster I becoming the dominant group (about 80%). A clone library of archaeal SSU rRNA gene fragments generated at 49°C was also dominated (10 out of 11 clones) by rice cluster I. Our results demonstrate that Italian rice field soil contains thermophilic methanogenic activity that was most probably a result of members of the as yet uncultivated euryarchaeotal rice cluster I.
Linking the composition of bacterioplankton to rapid turnover of dissolved dimethylsulphoniopropionate in an algal bloom in the North Sea
Authors: Zubkov Mikhail V. , Fuchs Bernhard M. , Archer Stephen D. , Kiene Ronald P. , Amann Rudolf , Burkill Peter H.
Published: March 2003

The algal osmolyte, dimethylsulphoniopropionate (DMSP), is abundant in the surface oceans and is the major precursor of dimethyl sulphide (DMS), a gas involved in global climate regulation. Here, we report results from an in situ Lagrangian study that suggests a link between the microbially driven fluxes of dissolved DMSP (DMSPd) and specific members of the bacterioplankton community in a North Sea coccolithophore bloom. The bacterial population in the bloom was dominated by a single species related to the genus Roseobacter, which accounted for 24% of the bacterioplankton numbers and up to 50% of the biomass. The abundance of the Roseobacter cells showed significant paired correlation with DMSPd consumption and bacterioplankton production, whereas abundances of other bacteria did not. Consumed DMSPd (28 nM day−1) contributed 95% of the sulphur and up to 15% of the carbon demand of the total bacterial populations, suggesting the importance of DMSP as a substrate for the Roseobacter‐dominated bacterioplankton. In dominating DMSPd flux, the Roseobacter species may exert a major control on DMS production. DMSPd turnover rate was 10 times that of DMS (2.7 nM day−1), indicating that DMSPd was probably the major source of DMS, but that most of the DMSPd was metabolized without DMS production. Our study suggests that single species of bacterioplankton may at times be important in metabolizing DMSP and regulating the generation of DMS in the sea.
Identification of a microorganism that links its growth to the reductive dechlorination of 2,3,5,6‐chlorobiphenyl
Authors: Cutter Leah A. , Watts Joy E. M. , Sowers Kevin R. , May Harold D.
Published: March 2003

Anaerobic bacteria reductively dechlorinate polychlorinated biphenyls (PCBs) in aquatic sediments, but these microorganisms remain uncultured and, until now, unidentified. Through denaturing gradient gel electrophoresis (DGGE) of 16S rDNA from a highly enriched ortho‐PCB dechlorinating culture, the growth of a single microorganism was shown to be dependent upon the presence and dechlorination of 2,3,5,6‐tetrachlorobiphenyl. This is the first identification of a microorganism that catalyses the reductive dechlorination of a PCB. The organism, bacterium o‐17, has high sequence similarity with the green non‐sulphur bacteria and with a group that includes Dehalococcoides ethenogenes. Bacterium o‐17 required acetate for dechlorination and growth. H2:CO2 (80:20 at 101 kPa) did not support dechlorination or growth of the dechlorinator. Archaeal 16S rDNA was not detected in actively dechlorinating bromoethanesulphonate‐treated non‐methanogenic cultures, which indicated that methanogenic Archaea were not required for dechlorination. The consistent association with dechlorinating activity combined with high similarity to other known dechlorinating microorganisms indicates that bacterium o‐17 catalyses the reductive ortho‐dechlorination of 2,3,5,6‐tetrachlorobiphenyl.
Structure and carbohydrate analysis of the exopolysaccharide capsule of Pseudomonas putida G7
Authors: Kachlany Scott C. , Levery Steven B. , Kim John S. , Reuhs Bradley L. , Lion Leonard W. , Ghiorse William C.
Published: March 2003

The aromatic hydrocarbon‐degrading bacterium, Pseudomonas putida G7, produces exopolymers of potential interest in biotechnological applications. These exopolymers have been shown to have significant metal‐binding ability. To initiate the study of the metal–polymer interactions, we explored the physical and chemical nature of the P. putida G7 exopolysaccharide, a major component of the exopolymer. A capsular structure was observed by light microscopy surrounding both planktonic and attached cells in biofilms after immunofluorescence staining with polyclonal antiserum raised against planktonic cells. Further work with planktonic cells showed that the immunostained capsule remained associated with young (log phase) cells, whereas older (stationary phase) cells lost their capsular material to the external milieu. Visualization of frozen, hydrated stationary phase cells by cryo‐field emission scanning electron microscopy (cryoFESEM) revealed highly preserved extracellular material. In contrast, conventional scanning electron microscopy (SEM) of stationary phase cells showed rope‐like material that most probably results from dehydrated and collapsed exopolymer. Both capsular and released exopolymers were separated from cells, and the released extracellular polysaccharide (EPS) was purified. Deoxycholate–polyacrylamide gel electrophoresis (PAGE) and silver/alcian blue staining of the partially purified material showed that it contained both EPS and lipopolysaccharide (LPS). Further purification of the EPS using a differential solubilization technique to remove LPS yielded highly purified EPS. Gas chromatography–mass spectrometry revealed that the purified EPS contained the monosaccharides, glucose, rhamnose, ribose, N‐acetylgalactosamine and glucuronic acid. The structural and chemical properties of the P. putida EPS described here increase our understanding of the mechanisms of toxic metal binding by this well‐known Proteobacterium.
Microbial community of a saline mud volcano at San Biagio‐Belpasso, Mt. Etna (Italy)
Authors: Yakimov Michail M. , Giuliano Laura , Crisafi Ermanno , Chernikova Tatyana N. , Timmis Kenneth N. , Golyshin Peter N.
Published: March 2003

In San Biagio of Belpasso, approximately 20 km south of Mt. Etna, in the area of contact between volcanic and sedimentary formations, a number of small (3– 60 cm in diameter) active mud eruptions discharge CO2‐rich gases, mud
and NaCl brines. They can be described as mini‐volcanoes owing to their typical conic
shapes and continuously bubbling peak craters. Samples were collected from the active
peak craters at a depth of 20 cm and DNA was immediately extracted and amplified
with universal 16S rRNA gene‐specific primers, followed by cloning procedure. A total
of 140 bacterial clones obtained were screened and clustered by restriction fragment
length polymorphism (RFLP) analysis. The pool of 16S rRNA sequences representing
each RFLP cluster was subjected to phylogenetic analysis. All of the 33 sequences
analysed were affiliated with the kingdom of Eubacteria; 28 sequences (77%
of all clones) affiliated with the Proteobacteria, two sequences (19%
of all clones) were affiliated with Actinobacteria and three sequences (4%
of all clones) were affiliated with the Flexibacter‐Cytophaga‐Bacteroides
division. The data obtained suggest that the microorganisms phylogenetically affiliated
to autotrophic methane oxidizers and heterotrophic hydrocarbon degraders belonging
to the gamma‐subclass of Proteobacteria are major constituents of the microbial communities of the saline volcanic muds. Overall, the composition of the microbial community of the San Biagio mud volcano resembles the compositions of marine microbial communities, which might indicate that wind‐blown seawater vapour acted as an inoculum for microbial community described in present work.
Prokaryotic phylogenetic diversity and corresponding geochemical data of the brine–seawater interface of the Shaban Deep, Red Sea
Authors: Eder Wolfgang , Schmidt Mark , Koch Marcus , Garbe‐Schönberg Dieter , Huber Robert
Published: March 2003

The interface between the hypersaline brine and the overlying sea‐water (brine–seawater interface) of the Shaban Deep, northern Red Sea was investigated for the presence of microorganisms using the 16S rRNA gene as a molecular marker. Samples of the south and east basin (depth: 1331 m and 1332 m respectively) were selected to ascertain the microbial diversity of this extreme and, so far, unexplored environment. Phylogenetic analysis revealed novel lineages within the Bacteria, the Crenarchaeota and the Euryarchaeota. Novel representatives of the KB1 sequence group (Eder et al., 1999 Arch Microbiol 172: 213–218) were detected indicating a widespread distribution of the corresponding Bacteria in Deep Sea brine pools. Our results contribute to the understanding of the hitherto unknown microbial diversity at the chemical gradient of the Shaban Deep, and suggest the presence of novel Bacteria and Archaea thriving under extreme environmental conditions.
Alkane hydroxylase homologues in Gram‐positive strains
Authors: Van Beilen Jan B. , Smits Theo H. M. , Whyte Lyle G. , Schorcht Susanne , Röthlisberger Martina , Plaggemeier Thorsten , Engesser Karl‐Heinrich , Witholt Bernard
Published: March 2003

We isolated Gram‐positive alkane‐degraders from soil and a tricking‐bed reactor, and show using polymerase chain reaction (PCR) with degenerate alkane hydroxylase primers and Southern blots that most Rhodococcus isolates contain three to five quite divergent homologues of the Pseudomonas putida GPo1 alkB gene. Two Mycobacterium isolates each contain one homologue, however there is no evidence for the presence of alkB homologues in the remaining strains.
Colectomy and ileorectal anastomosis or restorative proctocolectomy for familial adenomatous polyposis
Authors: Heiskanen  , Matikainen  , Hiltunen  , Laitinen  , Rintala  , Järvinen
Published: March 2003

The choice of prophylactic operation for familial adenomatous polyposis (FAP) is controversial. Colectomy and ileorectal anastomosis (IRA) is a time‐honoured procedure but has recently been replaced by restorative proctocolectomy in many centres. The objective of this study was to compare the operative and functional outcomes following IRA and restorative proctocolectomy (RPC). The morbidity rate, operation time, blood loss and hospital stay were compared in 99 IRA and 33 RPC patients. The functional outcome following IRA and RPC were compared in 22 sex‐matched pairs. The median hospital stay was 11 days after IRA and 12 days after RPC. The operation time was longer in RPC (216 vs 182 min) and blood loss greater (1253 vs 634 ml). The complication rates were 30% after RPC and 18% after IRA. None of 23 primary RPC operations failed, but two (20%) of the 10 patients with secondary RPC following IRA finally received a permanent ileostomy. The overall functional satisfaction was excellent in 82% and 88% after RPC and IRA, respectively. The mean basal anal pressure was higher in the IRA groups (54 vs 39 cmH2O, P = 0.004) and the stool frequency slightly less (4.7 vs 5.8, P = 0.06) than after RPC. There is little difference in short‐term surgical or functional results between IRA and RPC but a secondary RPC may be unsuccessful. Therefore, primary RPC may be a better option in FAP than IRA.
Histopathologic characteristics of advanced colorectal cancer smaller than 2 cm in size
Authors: Adachi  , Yasuda  , Kakisako  , Sato  , Shiraishi  , Kitano
Published: March 2003

Purpose

Screening for colorectal cancer results in an increased incidence of early detection and decreased mortality. Although small colorectal cancer with deep invasion or lymph node metastasis is sometimes encountered, there is no comprehensive study evaluating the histopathologic features of such tumours. The aim of this study was to clarify the characteristics of advanced colorectal cancer <2 cm in size.

Methods

Using a series of 317 patients who underwent surgery for colorectal cancer, pathologic features were compared among small advanced cancers <2 cm invading the muscularis propria or subserosa (T2, T3) or involving the lymph nodes (N1, N2) (n = 22), small early cancers <2 cm invading only the mucosa or submucosa (T1) without lymph node metastasis (N0) (n = 24), and ordinary advanced cancers> 2 cm (n = 271).

Results

Small advanced cancers were clearly different from small early cancers in gross appearance, histological type, frequency of serosal invasion (18% vs 0%, P < 0.05), lymph node metastasis (36% vs 0%, P < 0.01), and concomitant adenomatous component (17% vs 48%, P < 0.05). Small advanced cancers, when compared with ordinary advanced cancers, were characterized by the grossly superficial type (14% vs 1%, P < 0.01) and absence of serosal invasion (82% vs 14%, P < 0.01) However, the two groups were not significantly different with regard to the frequency of lymph node metastasis (36% vs 53%), liver metastasis (5% vs 15%), and stage of the disease (Dukes’ A and B; 64% vs 45%).

Conclusion

The results indicate that colorectal cancers, once they invade beyond the submucosa, have the same metastatic potential, irrespective of tumour size. The low frequency of concomitant adenoma implies de novo carcinogenesis of the small advanced cancers.
Quantitative radio‐isotope proctography—a new technique for the assessment of rectal evacuation
Authors: Vijaya‐Sekaran  , Nguyen  , Groom  , Levitt
Published: March 2003

Objective

 The aim of this study was to establish a technique for measuring both the efficiency and speed of rectal evacuation and to assess the impact on these parameters of varying the volume of instillate.

Subjects and methods

 Twelve healthy volunteers had 100 ml, 150 ml and 200 ml of isotope‐labelled paste inserted into the rectum on three separate occasions and asked to evacuate the paste on a modified commode. Radioactivity within the rectal field was measured at 2‐s intervals. The speed of evacuation from both the time at which the command to evacuate was given and the time at which evacuation commenced and efficiency of evacuation were calculated.

Results

 The efficiency of evacuation differed little with the changing volumes of instillate (median values 69%, 68% and 67% for 100 ml, 150 ml and 200 ml, respectively). The speed of evacuation increased with increasing volumes of instillate and was significantly faster when comparing the 200‐ml group with the 100‐ml group (Wilcoxon rank sum test for paired data, P < 0.05). The increase in speed of rectal emptying was, however, due to earlier initiation of evacuation rather than a faster rate of rectal emptying.

Conclusions

 The findings suggest that quantitative tests of rectal emptying should use a set volume of instillate to avoid variations in the speed of evacuation and indicate that a larger volume of instillate may be preferable to smaller volumes for the purposes of testing rectal emptying.
Chronic anal fissures treated with botulinum toxin injections: a dose‐finding study with Dysport®
Authors: Jost  , Schrank
Published: March 2003

Botox® injection of the anal sphincter muscle cures chronic uncomplicated anal fissures in up to 80% of patients. This study examines the therapeutic efficacy and side effect profile of the British botulinum product Dysport®. Fifty patients (29 women) were recruited to participate in this randomized dose‐finding study, their mean age being 32.9 years. The low dose group A was treated with a total dose of 20 U injected in two sites each lateral to the fissure, the high dose group B was treated with 40 U. Eighty‐two percent of patients were pain‐free within a week following the injections. The fissure was healed in 78% of treated patients after 3 months. Three patients relapsed within 6 months. The most common adverse side effect was transient incontinence (n = 4). Clinical outcome was not significantly different between the two treatment groups. The low dose can therefore be regarded sufficient for the treatment of anal fissure. Therapeutic efficacy was equivalent to published data on Botox treatment. Both Dysport® and Botox® can therefore be used to treat chronic uncomplicated anal fissures. Both Dysport® and Botox® therapy are well tolerated, can be performed on an out‐patient basis and avoid the risk of permanent faecal incontinence which complicates surgical treatment of anal fissures.
Biofeedback for anismus: has placebo effect been overlooked?
Authors: Meagher  , Sun  , Kennedy  , Smart  , Lubowski
Published: March 2003

Objective

Multiple uncontrolled studies have concluded that biofeedback is successful in treating anismus. This study’s objective was to assess the physiological effects of placebo and biofeedback treatment on patients with anismus and to correlate changes with clinical improvement.

Patients and methods

Twelve patients with symptoms and electrophysiological findings of anismus were studied. Initial assessment included a detailed history, symptom assessment by linear analogue scales, anorectal manometric and electrophysiological studies, colon transit scintigraphy, and scintigraphic proctography. Patients underwent 5 days of placebo treatment, followed 1 week later by re‐assessment of symptoms and physiological studies. Five days of biofeedback was then given followed by another complete re‐assessment 1 week later. A final interview was performed 2 months later. All assessments were by an independent observer who was not responsible for the treatments.

Results

Seven patients reported an overall improvement in symptoms following placebo treatment. A total of seven patients reported improvement following biofeedback, three of whom had already reported an improvement with placebo. One patient who reported improvement following placebo had worsening of symptoms following biofeedback. The only symptoms or tests which changed more with biofeedback than placebo were anal pressure and electromyographic activity on attempted defaecation in the left lateral position. There was no demonstrable correlation between change in symptoms and change in physiological tests. The scintigraphic ‘ejection fraction’ of the rectum was unchanged by treatment.

Conclusion

Clinical improvement in previous studies may in part be due to placebo effect and observer bias. Improvement with biofeedback may be due to physiological changes which are not detected with conventional anorectal physiological tests.
Guidelines for the surveillance and management of familial adenomatous polyposis (FAP): a world wide survey among 41 registries
Authors: Vasen  , Bülow  ,   The Leeds Castle Polyposis Group
Published: March 2003

Objectives

 FAP is an autosomal dominant disease characterized by numerous adenomas in the colorectum. The majority of patients also develop adenomas in the duodenum. The purpose of the study was to evaluate the management and screening protocols implemented in FAP families at various polyposis registries in the world.

Methods

 A questionnaire was mailed to the members of The Leeds Castle Polyposis Group requesting information on: diagnostic evaluation of polyposis, recommendations for screening and surgical management of the colon, surveillance of the upper gastrointestinal tract and the management of duodenal polyposis.

Results

 Almost all members agreed that a newly diagnosed patient should be referred to a polyposis registry and to a clinical genetics centre for genetic counselling and DNA testing. If the mutation has been detected in the family, DNA testing should be offered to first‐degree relatives of patients from age 10–12 years onwards. The surveillance protocol generally advised includes sigmoidoscopy from age 10–12 years at 2‐year intervals until age 40 years. There was no agreement on the preferred surgical treatment of colonic polyposis. Almost all members advised follow up after colonic surgery. Surveillance of the duodenum was recommended by most members; this would start from age 30 years. There was no agreement on the preferred surgical treatment of duodenal polyposis, or on the indication for operation.

Conclusion

 This survey provides insight into the guidelines used at various polyposis registries for the surveillance and management of FAP patients, and this insight may contribute to the appropriate management of these patients.
The significance of hyperamylasaemia after colonic resection
Authors: Griffith  , Eu  , Leong  , Ho  , Nyam  , Seow‐Choen
Published: March 2003

Objective

Colonic resection may be complicated by prolonged post‐operative paralytic ileus. Post‐operative hyperamylasaemia and pancreatitis may sometimes follow abdominal surgery or occasionally trauma. Post‐operative ileus seen after colectomy may be secondary to unrecognized pancreatitis and hyperamylasaemia. The aims of this study were to identify the incidence of hyperamylasaemia after colonic resection, to investigate the effect of hyperamylasaemia on post‐operative intestinal function and to correlate any changes with extent of colorectal resection.

Patients and methods

The serum amylase was determined prospectively in a consecutive series of 150 patients who underwent elective colorectal resection. Serum amylase was measured before surgery and post‐operatively until it returned to within the normal range.

Results

Hyperamylasaemia occurred in 28 patients (18.7%) after colorectal surgery. Serum amylase levels returned to normal in all but seven patients (4.7%) by the second post‐operative day. The development of hyperamylasaemia did not adversely influence the post‐operative course. Both groups of patients had similar restoration of intestinal function and were discharged home on equivalent days. Ligation of the middle colic artery alone was found to be significantly associated with hyperamylasaemia by multivariate stepwise logistic regression analysis.

Conclusion

Twenty‐eight out of 150 patients who underwent colorectal resection developed hyperamylasaemia after surgery. The incidence was highest in patients with middle colic artery ligation. The development of post‐operative hyperamylasaemia does not seem to influence adversely the post‐operative course in this series.