Alcaligenes faecalis

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### **Overview**

*Alcaligenes* faecalis *is a species of Gram-negative, rod-shaped bacteria commonly found in* the environment. It was originally named for its first discovery in feces, but
was later found to be common in soil, water, and environments in association
with humans. While opportunistic infections do occur, the bacterium is generally considered non-pathogenic. When an opportunistic infection does occur, it is usually observed in the form of a urinary tract infection.

Alcaligenes faecalis is a species of Gram-negative,
rod-shaped bacteria commonly found in the environment. It was originally named
for its first discovery in feces, but was later found to be common in soil,
water, and environments in association with humans. While opportunistic
infections do occur, the bacterium is generally considered non-pathogenic. When
an opportunistic infection does occur, it is usually observed in the form of a
urinary tract infection.

*Alcaligenes faecalis* occur in water and soil.
The microbe has peritrichous flagellar arrangement which allows for motility (2). It is a gram-negative, rod-shaped organism observed at 0.5-1.0 μm x 0.5-2.6 μm in diameter. An aerobic microbe, *A. faecalis* is optimal
at temperatures between 20-37 °C (11).

This microbe is most commonly seen in the clinical
laboratory. Most infections caused by *A. faecalis* are
opportunistic and acquired from moist items such as nebulizers, respirators,
and lavage fluids. When an infection occurs, it is usually in the form of a
urinary tract infection (2). However, *A. faecalis* is also
known to be the pathogen that causes bacterial keratitis and postoperative endophthalmitis. Numerous strains have been isolated from clinical material
such as blood, urine and feces (11).

A study on metabolic energy observed *Alcaligenes*
faecalis*surviving in cultures of 10 g/L of aqueous arsenic. The*
survival of the microbe in arsenic is important in bioremediation of
environments contaminated with aqueous arsenic (12). In environments with high
arsenic, the community must be wary of the likely presence of *A.* faecalis*and its tendency to cause infections.*

### **Cell structure and** **metabolism**

As *Alcaligenes faecalis* is a gram-negative
bacterium, it possesses an outer membrane (composed of lipopolysaccharides, phospholipids, and proteins), a thin peptidoglycan layer, and a periplasm. These three layers form the gram-negative cell envelope.

*A. faecalis* is unusual among gram-negative
bacteria for it's ability to aerobically desaturate saturated fatty acids in order to produce monounsaturated fatty acids (3). Higher-order organisms such as
animals, protozoa, and various types of algae have this ability, while most
bacteria and almost all gram-negative bacteria use an anaerobic pathway. *A.*
faecalis*has also demonstrated the ability to enzymatically metabolize* arsenite (AsO2-, oxidation state +3) to the less harmful arsenate (AsO4-, oxidation state +5). This bacterium
could be useful for neutralization of environments contaminated by arsenite.

*A. faecalis* is a heterotrophic denitrifier, meaning that it breaks down NO3, NO2-, and NH4+ using
organic C as an carbon and energy source. The mechanism of NO2- conversion
to NO by *A. faecalis* has been attributed to nitrite reductase, a copper-containing enzyme (13). In some ecosystems, much of the atmospheric NO
and N2O produced by soil bacteria is a product of heterotrophic
nitrification (10).

### **Ecology**

**Figure 4**--***Alcaligenes faecalis*** **Environment**
The human alimentary canal is inhabited by *Alcaligenes faecalis*. Diagram by UCLA Health
System Transplantation Services (16).

*Alcaligenes faecalis* is an aerobic bacillus known to inhabit soil and water environments (5). Optimal temperature for the
microbe ranges from 20 °C to 37 °C (11). *A. faecalis* also inhabits the alimentary canal of humans (5).

This microbe is known to contaminate medical devices in the
clinical environment, which can lead to infection. In the human eye, *A.*
faecalis*is likely a cause of postoperative endophthalmitis, and it*
has been isolated from corneal ulcers (6). Kahveci *et al*. (2011)
found that contamination of peritoneal dialysis catheters with the microbe may
be linked to patients developing peritonitis (5).

The microbe has been isolated from human bodily fluids in
association with both open wounds and ear discharge. *A. faecalis* has also been found in feces (6).

Recently, researchers have shown that a biosurfactant produced by *Alcaligenes faecalis* may be a promising agent to bioremediate oil spills (3).

### **Pathology**

*Alcaligenes faecalis* exists in the alimentary
canal, but systemic infections with the microbe do not occur in the majority of
healthy humans. Infections caused by *A. faecalis* have been
observed in humans with compromised immune systems and uncompromised immune systems. Many infections caused by the microbe are a result of contamination of
medical devices. (5)

Kaliaperumal *et al.* (2006) have shown
that *A. faecalis* may be a causative agent in postoperative
endophthalmitis in the human eye (see figure 2). Infection with the microbe
likely stems from exposure to other parts of the body or contaminated
instruments. (6) Patients on endophthalmitis may experience swelling of the eyelid,
redness, and permanent loss of vision (15).

Kahveci *et al.* (2011) found that catheters
contaminated with *A. faecalis* may be associated with
development of peritonitis in peritoneal dialysis patients. Symptoms of
peritonitis include vomiting, passing little or no stool, sore and bloated
abdomen, and fever. (14)

The microbe has been found to cause urinary tract infections
in humans (2). In addition, *A. faecalis* has been found in
corneal ulcers, feces, blood, and other bodily fluids (6).

In addition to infecting humans, *A. faecalis* is a pathogen of domesticated chickens, domesticated turkeys, and other birds.
Simmons *et al.* (1980) were able to isolate *A. faecalis* from
broiler chicks, and it was likely related to respiratory disease in the chicks
(7).

Although *A. faecalis* has been isolated from
human and non-human hosts, the pathogenic mechanism of the microbe is largely
unknown. Many of the studies investigating the virulence of the microbe have
been conducted on mammalian and avian species, and some of the proposed
mechanisms may be carried out in human hosts. (6)

### **Genome structure**

'*Genes for the arsenite oxidase region in*A.
faecalis
Presumed gene product lengths (in amino acids [aa]) and functions are
indicated. Diagram by Silver
and Phung (7).

Despite its relevance to the medical field, the complete
genome of *Alcaligenes faecalis*, or any of the *Alcaligenes* species,
has not been sequenced.

Only parts of the *A. faecalis* genome have
been sequenced by researchers. Silver and Phung (2005) sequenced a 71-kb linear *A. faecalis* DNA region responsible for encoding
arsenite oxidase as well as associated functions. More than 20 genes are
located in this region, forming a "gene island" responsible for
arsenic oxidation, resistance, and metabolism. These include a large molybdopterin-containing peptide subunit and a small [2Fe-2S] subunit, both
responsible for arsenic oxidase.

Plasmid DNA encoding virulence and resistance has been
identified in *A. faecalis* (9).

### **Current Research**

* ***Crude***

 biosurfactant from thermophilic *Alcaligenes faecalis*:
 Feasibility in petro-spill bioremediation***(3)***
Petroleum hydrocarbons are major environmental pollutants. Bioremediation at the site of contamination is considered an environmentally
friendly means of petroleum hydrocarbon clean-up. Natural biodegradation in the
environment is limited by the hydrophobic properties of hydrocarbons. Bharali *et al.* explored the use of *A. faecalis* to
promote biodegradation of petroleum hydrocarbons (3).

*A. faecalis* produces biosurfactant compounds
that increase the hydrophobicity of the cell surface during growth on hydrocarbons
that enhances the contact with the hydrocarbons and as a result increases
hydrocarbon degradation. The capacity to produce biosurfactant was studied by growing *A. faecalis* in salt media with a variety of
hydrophobic substrates (diesel, kerosene, crude oil) as the carbon source.
Under different substrate concentrations, surface tension and the rate of
biosurfactant production was measured.

It was found that the biosurfactant produced by *A.*
faecalis*possessed high surface activity, decreasing surface tension*
adequately to allow for degradation by the microorganism. In addition to the
surface activity of the biosurfactant, it was found to be stable over high
temperatures, a range of pH and different salt concentrations, and also
possessed antimicrobial properties against a variety of bacteria and fungi. The
versatile nature of the biosurfactant produced by *A. faecalis* makes *A.*
faecalis*an excellent candidate for use in bioremediation of* hydrocarbon pollution such as oil spills.(3)

* ***Improvement***

 in ammonium removal efficiency in wastewater treatment by mixed culture
 of *Alcaligenes faecalis* No. 4 and L1***(4)*** Ammonium removal is a required step in the treatment of
wastewater. Typically this process is completed by the use of autotrophic nitrifiers and heterotrophic denitrifiers in two separate (aerobic and
anaerobic) tanks. The growth of autotrophic nitrifiers is very slow requiring a long hydraulic retention time in treatment plants. *Alcaligenes faecalis* has
been identified as a heterotrophic nitrifier and aerobic denitrifier and
converts ammonium into denitrification products simultaneously. Unfortunately the ammonium removal rate of heterotrophic nitrifiers is lower than that of autotrophic nitrifiers, alternatively the growth of heterotrophic bacteria is
faster than that of autotrophs.

Joo *et al* (2006) explored the efficiency of a strain of *A. faecalis* with high denitrification behavior
isolated from their laboratory called *A. faecalis* no. 4, combined with a mutant strain of *A. faecalis*, L1, that has a higher
ammonium removal rate and a weaker denitrification ability than no. 4 in wastewater treatment. The aim of the study was to confirm the improved
efficiency of the mixed culture that takes advantage of the high ammonium removal capacity of L1 and the high denitrification capacity of no. 4.

Joo examined the change in efficiency by comparing the
ammonium removal and denitrification by the combined L1 and no. 4 cultures with
single cultures of each strain. Joo found that in the mixed culture the
ammonium removal rate was twofold higher than that in a single culture of no. 4
and similar to the rate in the single culture of L1. The denitrification rate
of the combined culture was exceptionally high compared to the single culture of L1. In addition to the improved ammonium removal, Joo found that the number of viable cells in the mixed culture decreased compared to the single cultures
resulting in reduced sludge production, the accumulation of which is a major
challenge in wastewater treatment by microorganisms. Joo *et al* concluded
that the combined single tank use of *A. faecalis* strains L1 and no. 4 is an improved alternative to the current methods of ammonium removal
in wastewater (4).

### **Interesting Fact**

Peritonitis (inflammation of the thin tissue that lines the
inner wall of the abdomen and covers most of the abdominal organs) is commonly
found in peritoneal dialysis (PD) patients due to contamination of the dialysis
catheter. The most common pathogens causing peritonitis in PD patients are gram
positive (*Staphylococcus epidermidis* and *Staphylococcus*
aureus*). Recently there have been unusual cases of*A. faecalis*causing*
peritonitis in PD patients. *A. faecalis* is not only a Gram
negative bacterium but also an environmental organism. Both of these
characteristics are rarely found to cause such significant infections and has
since been identified as a pathogen of consideration in the treatment of
clinical peritonitis cases.(5)

### References

1. Clark, W. (1976). *Alcaligenes faecalis.* Leifson flagella stain (digitally colorized). CDC Public Health Image Library

2. Winn, W., Sommers, H., Koneman, E., Janda, W., Dowell, V., and Allen, S (1988). "Color Atlas and Textbook of Diagnostic Microbiology". 'J.B. Lippincott Company'. Edition 3: 184, 200-201.

3. Bharali, P., Das, S., Konwar, B.K., and Thakur, A.J. (2001) Crude biosurfactant from thermophilic *Alcaligenes faecalis*: Feasibility in petro-spill bioremediation. Internation Biodeterioration & Biodegradation 65: 682-690.

4. Joo, H., Hirai, M., and Shoda, M. (2006) Improvement in ammonia removal efficiency in wastewater treatemnt by mixed culture of *Alcaligenes faecalis* No. 4 and L1. Journal of Bioscience and Bioengineering. 103(1): 66-73.

5. Kahveci, A., Asicioglu, E., Tigen, E., Ari, E., Arikan, H., Odabasi, Z., and Ozener, C. (2011) Unusual causes of peritonitis in a peritoneal dialysis patient: Alcaligenes faecalis and Pantoea agglomerans. Annals of Clinical Microbiology and Antimicrobials 10: 12.

6. "Kaliaperumal, S., Srinivasan, R., Gupta, A., and Parija, S.C. (2006) Postoperative endophthalmitis due to an unusual pathogen: *Alcaligenes faecalis*. Eye 20: 968–969."

7. "Simmons, D., Davis, D., Rose, L., Gray, J., and Luginbuhl, G. (1980) "*Alcaligenes faecalis*"-Associated Respiratory Disease of Chickens. Avian Diseases 25(3): 610-613."

8. Silver, S. & Phung, L.T. (2005) Genes and Enzymes Involved in Bacterial Oxidation and Reduction of Inorganic Arsenic. Applied and Environmental Microbiology 71(2): 599-608.

9. Luginbuhl, G.H., Rader, J.M., and Simmons, D.G. (1984). Evidence for plasmid DNA in *Alcaligenes faecalis*. Am J Vet Res 45(8): 1679-81.

10. Anderson, I.C., Poth, M., Homstead, J., Burdige, D. (1993). A Comparison of NO and N20 Production by the Autotrophic Nitrifier *Nitrosomonas europaea* and the Heterotrophic Nitrifier *Alcaligenes faecalis*. Applied and Environmental Microbiology 59(11): 3525-3533.

11. Austin, B., Colwell, R.R., Forns, J.M., and Rodgers, C.J. (1981). *Alcaligenes faecalis* subsp. homari subsp. nov., a new group of bacteria isolated from moribund lobsters. International Journal of Systematic Bacteriology 31(1): 72-76.

12. Muller, D., Médigue, C., Koechler, S., Barbe, V., Barakat, M., Talla, E., & ... Makita, Y. (2007). A Tale of Two Oxidation States: Bacterial Colonization of Arsenic-Rich Environments. Plos Genetics, 3(4): 53-66.

13. Murphy M.E., Turley S., Kukimoto M., Nishiyama M., Horinouchi S., Sasaki H., Tanokura M., Adman E.T. (1995). Structure of *Alcaligenes faecalis* nitrite reductase and a copper site mutant, M150E, that contains zinc. Biochemistry 34(38): 12107-17.

14. Bhimji, S. Peritonitis. PubMed Health. U.S. National Library of Medicine. Web. 20 Oct. 2011.

15. Egan, D.J. & O'Connor, E.C. (2011). Endophthalmitis. Medscape Reference. Medscape. Web. 20 Oct. 2011.

16. Intestinal Transplant/GI Tract. UCLA Health System Transplantation Services. University of California, Los Angeles. Web. 20 Oct. 2011.

* **Created and Edited by** ***Kevin Wieczerza, Stephanie Freed, Amanda McKenzie, Hughes Burridge*** -- **Students of** ***Dr. Iris Keren from Microbewiki.kenyon.edu***
* May contain edits and alterations to reflect new information