Lactobacillus salivarius

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1. Classification

a. Higher order taxa

Lactobacillus salivarius belongs to the terrabacteria group in the class Firmicutes. It is in the class Bacilli, of the order Lactobacillales, and belongs to the family Lactobacillus (“European Bioinformatics” 2018).

2. Description and significance

Lactobacillus salivarius is a well characterized, rod-shaped, Gram-positive species of probiotic bacteria (Chapot-Chartier et al. 2014). It is commonly isolated from human, porcine, and avian gastrointestinal tracts. L. salivarius is a lactic acid bacterium that has antimicrobial activity due to the production of bacteriocins, which directly inhibit pathogens (Messaoudi et al. 2013). Modern discoveries have demonstrated the effectiveness of the bacteriocins of L. salivarius against specific pathogens such as those that are responsible for foodborne illness, acne and other skin conditions, and irritable bowel syndrome in humans (Messaoudi et al. 2013, Corr et al. 2007, Deidda et al. 2018, Peran et al. 2005). L. salivarius has also been proven to fight the pathogen Staphylococcus aureus; L. salivarius can target both planktonic cells as well as biofilms of S. aureus through the secretion of anti-Staphylococcus proteins. (Kang et al. 2017) The bacteriocin properties of L. salivarius also are effective in food preservation (Messaoudi et al. 2013). New knowledge regarding the beneficial antibacterial properties of L. salivarius have led to an increase in the use of the strain as a replacement to previous topical and oral antibiotics (Corr et al. 2007). Further exploration of the mechanisms of L. salivarius’ probiotic and antimicrobial properties has the potential to yield new discoveries beneficial to human health.

3. Genome structure

The genome of L. salivarius is a circular chromosome of approximately 2,028,405 base pairs with a 32.7% G/C content (Ayala et al. 2017). Of all of the chromosomal genes, the function of 71% of these genes are known (Claesson et al. 2006). There are 1,982 protein coding sequences along with 64 tRNA and 31 rRNA sequences (Ayala et al. 2017). Additionally, this bacterial genome has a tetracycline resistance gene (Ayala et al. 2017). Of the entire genome of L. salivarius, 20% consists of four plasmids, two of which are megaplasmids (Raftis et al. 2014, Seol et al. 2011). Evidence shows these megaplasmids may be a possible mechanism used by the bacterium to expand and/or contract its genome to adjust to varying environmental conditions (Claesson et al. 2006). One of the megaplasmids identified encodes proteins involved in metabolic processes and expresses characteristics that can help L. salivarius survive within the gastrointestinal tract of humans (Claesson et al. 2006). However, the function of only 50% of the genes of the megaplasmid are known (Claesson et al. 2006).

4. Cell structure

Interesting features of cell structure. Can be combined with “metabolic processes”

5. Metabolic processes

Describe important sources of energy, electrons, and carbon (i.e. trophy) for the organism/organisms you are focusing on, as well as important molecules it/they synthesize(s).

6. Ecology

Habitat; symbiosis; contributions to the environment.

7. Pathology

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

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.