Actinomyces gerencseriae

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1. Classification

a. Higher order taxa

Domain: Bacteria
Phylum: Actinobacteria
Class: Actinobacteria
Order: Actinomycetales
Family: Actinomycetaceae
Genus: Actinomyces
Species: Actinomyces gerencseriae

2. Description and significance

Actinomyces is a genus of bacteria that consists of a widely varied number of species that can exist both in the soil microbiome as well as within human and animal bodies. The Actinomyces genus mostly consists of Gram-positive bacilli that are facultatively anaerobic or microaerophilic rods. ¹ Species from the Actinomyces genus often live primarily within the oral cavities of humans as part of the natural endogenous microbiome, but can become pathogenic when they are able to enter the body through open wounds, such as those stemming from poor dental hygiene. Members of the Actinomyces genus are significant because certain species (primarily A. gerencseriae and A. israelii) are known to cause the disease actinomycosis. Actinomycosis is a chronic and inflammatory granulomatous infection. This infection is referred to as granulomatous due to the granuloma, or inflammation, caused by an accumulation of macrophage immune cells that is a reaction of the host body to the invading pathogen. Actinomycosis can result in abscesses in the mouth, lungs, breast, and gastrointestinal tract in humans. While the incidence of this disease is rare, it can be particularly detrimental if and when it spreads to other tissues.

3. Genome structure

Actinomyces gerencseriae possesses a GC-rich genome, composed of 70% GC pairs.

The strain type of A. gerencseriae is ATCC 23860 = CCUG 32936 = CCUG 34703 = CDC W 838 = CIP 105418 = DSM 6844 = JCM 12963 = VPI 12594. ²

4. Cell structure

The entirety of the Actinomyces genus consists of gram positive bacteria. These gram positive bacilli bacteria possess cell walls consisting of a large external peptidoglycan layer threaded with teichoic acids and lipoteichoic acids. This peptidoglycan layer is separated from the cell membrane bilayer by the periplasmic space. The cell membrane bilayer is interspersed with important membrane proteins.

When Actinomyces was initially discovered in the late 1800s as a source of oral infection first in cows (A. Bovis) and then humans (A. Israelii), it was mistakenly identified as a fungal genus. The reason for this was the tendency for Actinomyces species to grow in a filamentous manner, and form hyphaes similar to eukaryotic fungi. Although this has been the typical classification of Actinomyces, several more recently discovered of these species lack the ‘typical’ branching rod appearance. ³

Actinomyces gerencseriae is a nonmotile, Gram positive bacterial species. The average Actinomyces gerencseriae colony is around 0.2 mm in diameter, circular in shape, are branching filamentous and white in color. Actinomyces gerencseriae have an incubation period of 2 days and is a non-spore forming bacterial species.

5. Metabolic processes

The ability to metabolize certain substances is an important distinguishing factor for the different Actinomyces species. The primary tests used in research include the ability for nitrate reduction, CAMP test reaction, as well as tests for the production of β-galactosidase, β-NAG, β-xylosidase, and 𝛼-fucosidase. Esculin hydrolysis is also a useful test for distinguishing certain species within the genus. Actinomyces as a genus has also been found to produce lactic acid in addition to succinic acid.

A common problem in recent years after the determination of A. gerencseriae as a separate species from A. israelii has been the separation of the two on a biochemical basis. It has been discovered, however, that these two species can be distinguished by their differential abilities to ferment different metabolites. A. israelii was found to possess the ability to ferment arabinose, while A. gerencseriae cannot. ³ Additional research has showed that these two species show differing abilities in the degradation of two mannopyranoside isomers. A. israelii can degrade the β-mannoside isomer, while A. gerencseriae can degrade the 𝛼-mannoside isomer. ⁴

6. Ecology

The genus normally presents itself in the oral cavity. A study on biofilm growth of the Actinomyces species found that in the presence of Actinomyces gerencseriae, Lactobacillus plantarum and Lactobacillus rhamnosus grew 4-20 times more than in a presence of another bacterial species in the oral community. Lactobacillus plantarum and Lactobacillus rhamnosus are examples of bacterial species commonly found in the oral cavity of humans, and their accelerated growth in this case demonstrate that overall, A. gerencseriae promotes growth in its ecological niche. Actinomyces gerencseriae are primarily microaerophilic, though some strains appear to be anaerobic. The significance of research in this area reveals itself when the features of the Lactobacillus genus, which can tolerate and utilize lactic acid in plaque under anaerobic conditions, are coupled with the growth promoting effects of the Actinomyces genus. Actinomyces promoted the growth of lactobicilli by providing a biofilm matrix. ⁵

7. Pathology

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

7. Key microorganisms

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8. Current Research

Include information about how this microbe (or related microbes) are currently being studied and for what purpose

9. References

It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.