Gardenerella vaginalis

A Microbial Biorealm page on the genus Gardenerella vaginalis

Classification

Higher order taxa

Bacteria; Actinobacteria; Actinobacteridae; Bifidobacteriales; Bifidobacteriaceae; Gardnerella

Species

Gardnerella vaginalis

Description and significance

Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.

Gardnerella vaginalis, the only species of its genus and formerly known as Haemophilus vaginalis and Corynebacterium vaginale, is a facultative anaerobic, nonmotile, pleomorphic gram-negative to gram-variable rod. It is a well-recognized colonizer of the female genital tract and survives high pH(2). It also survives poorly in human urine at 37 degrees C (3).

Genome structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?

The G. vaginalis genome is a circular DNA that ranges between 1.67 Mb and 1.72 Mb in size, with a 42-44% G+C content.

Cell structure and metabolism

Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.

Gardnerella vaginalis is a gram-variable microbe, and therefore displays both, gram-negative and gram-positive bacteria characteristics. When analyzing a culture, it may appear gram positive during the exponential growth phase but gram negative as it ages because the peptidoglycan layer becomes too thin to retain the crystal-violet iodine aggregates(5). These organisms are surrounded by a exopolysaccharide layer and pili that aid in adhering to the epithelial cells of the vagina. The cell wall is comprised of straight chain saturated and unsaturated non-hydroxylated fatty acids with hexadecanoic acid and octadecenoic acid along with major amounts of alanine, glycine, glutamic acid and lysine(4). G. vaginalis has a very complex metabolism. Gardnerella vaginalis are facultative anaerobes, which means that they can metabolism glucose (and other simple sugars) in under both aerobic and anaerobic conditions. Under the aerobic metabolism of glucose, G. vaginalis forms lactic acid and acetic acid. However, under anaerobic conditions, the metabolism of glucose yields only lactic acid.

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Bacterial vaginosis (BV) is a polymicrobial, noninflammatory syndrome involving the lower genital tract that is characterized by a microecologic imbalance (including pH disturbance) and the replacement of lactobacilli-predominant flora with G. vaginalis, anaerobes, and Mycoplasma hominis. Microbial analysis has shown G. vaginalis to be the most causative agent but it exists in a symbiotic relationship with other anaerobes. Enzymes and decarboxylases produced by these anaerobic bacteria are thought to degrade proteins and convert the amino acids to amines. These amines raise the vaginal pH greater than 4.5 and produce a characteristic fishy odor and enhance the growth of Prevotella bivia. G. vaginalis adhere to squamous epithelium and appear to form "clue" cells under a microscope.

G. vaginalis is present in low concentrations in a healthy female but is present in extremely high concentrations in women with BV. Healthy women have high concentrations of Lactobaccilus crispatus and Lactobaccilus jensenii that produce hydrogen peroxide that keep harmful organisms from proliferating.

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

G. vaginalis is one of few microorganisms that cause Vaginal Bacteriosis. They are found in humans and some animals such as mares. Apart from the urinary and the bladder, they are also found in the endometrium, fetal membranes, and newborn infants and are caused by maternal infections, neonatal infections, and suppurative lesions.

Gardnerella vaginalis attaches better to urogenital squamous epithelial cells due to the exopolysaccharide layer and pili. And this attachment provides a means of migration from the genitourinary tract to the primary colonization site in the bladder. Women have squamous cells in their vagina and their bladder and these cells are absent in a man's bladder, therefore, they are less susceptible to this pathogen. The presence of clue cell-like squamous epithelial cells are observed in bladder urine by suprapubic aspiration in women affected with G. vaginalis and none are observed in men.

Some symptoms associated with vaginosis in women caused by G. vaginalis may include Gray, foul smelling vaginal discharge (the smell is particularly noticeable after intercourse, because semen is alkaline and reacts with the bacteria, causing the release of chemicals that produce the fishy smell), May have vaginal itching or burning, May have burning or discomfort on urination, May have pain with sexual intercours(5). Men may not have physical symptoms.

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

1. The American Journal of Obstetrics and Gynecology recently researched bacteriocin susceptibility of G. vaginalis and its relationship to biotype, genotype, and metronidazole susceptibility. Bacteriocin susceptibility of 36 G vaginalis clinical Isolates was tested against a vaginal strain of Lactobacillus acidophilus by a growth-inhibition method. The relationship to biotype, genotype, and resistance to metronidazole were analyzed by the chi (2) test and Fisher exact test. The isolates were classified as Biotype 5, 6, and 7. Biotype 5 was found in higher prevalence among the isolates resistant to bacteriocin than among the susceptible isolates. An association between biotype of G. vaginalis and an increased resistance to bacteriocin was found. The ability of G vaginalis to resist the antibacterial activity of Lactobacillus bacteriocin may be a pivotal factor in understanding bacterial vaginosis. This could help researchers determine what biotype to expect when dealing with high concentrations of G. vaginalis and avoid giving certain antibiotics.

2. A recent research at University of Udine, Italy tested to see if activation of vaginal hydrolytic enzymes, immunoglobulin A against G. vaginalis increases the risk of early preterm birth in women with bacterial vaginosis. Two hundred eighteen women in preterm labor with intact membranes had a vaginal Gram stain performed, and hydrolytic enzymes and IgA concentrations were determined. It was found that women with bacterial vaginosis had a significantly higher hydrolytic enzymes (sialidase and prolidase) concentrations than women with normal flora. Among women with bacterial vaginosis, those that had high concentrations of sialidase had a higher rate of early preterm birth whereas those with higher levels of prolidase and IgA did not pretict early preterm birth. The significant of this research is that it gives doctors to reduce preterm birth among women with bacterial vaginosis without fighting the extremely resistant G. vaginalis and by simply eliminating sialidase.

References

1. Joe Bischoff, Mikhail Domrachev, Scott Federhen, Carol Hotton, Detlef Leipe, Vladimir Soussov, Richard Sternberg, Sean Turner. "Gardnerella Vaginalis" <http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=2702>

2. S M Smith, T Ogbara, and R H Eng. "Involvement of Gardnerella vaginalis in urinary tract infections in men." J Clin Microbiol Volume 30. p. 1575–1577. <http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=265332>

Edited by Jaspreet Singh, student of Rachel Larsen