Lactobacillus johnsonii
A Microbial Biorealm page on the genus Lactobacillus johnsonii
Classification
Higher order taxa
Bacteria; Firmicutes; Bacilli; Lactobacillales; Lactobacillaceae; Lactobacillus
Species
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NCBI: Taxonomy |
Lactobacillus johnsonii
Description and significance
Lactobacillus johnsonii is one of the many microorganisms that reside in the human intestines. Like all species of the Lactobacillus genus, it is an anaerobic, Gram-positive bacteria, which has a rod-like shape and does not undergo spore formation (1). The human Gastrointestinal tract in which L. johnsonii resides is abundant with nutrients and relies upon more than 500 microbial species that inhabit it in order to develop and function properly. Specifically L. johnsonii and other GI tract microbes aid in polysaccharide and protein digestion and also generate a variety of nutrients, including vitamins and short-chain fatty acids that make up 15% of a human’s total caloric intake. In addition, because L. johnsonnii are able to undergo fermentation and can therefore make lactic acid, they play a major role in the fermentation and preservation of various food items, such as dairy, meat and vegetable, and cereal products (1, 2). Finally, L. johnsonii is characterized as being part of the “acidophilus complex” of the Lactobacillus genus. This complex is comprised of six Lactobacillus species that are thought to be involved in probiotic activities, meaning they are able to undergo processes that are beneficial to a human’s general health and well-being (2, 3). Such probiotic benefits particularly attributed to L. johnsonii include immunomodulation, pathogen inhibition, and epithelial cell attachment (2).
Genome structure
The genome of L. johnsonii strain NCC 533 was sequenced by the Nestle Research Center in Switzerland through the method of shotgun sequencing. The 1,992,676 base pair genome has a circular topology and is composed of 1,821 protein coding genes with 79 tRNAs (2, 4, 14). The Lactobacillus genus as a whole is characterized by its low Guanine+Cytosine content. L. johnsonii, in particular, contains a G+C content of 34.6% (2). Interestingly, L. jonsonii contains no genes which encode for the biosynthetic pathways necessary to generate amino acids and necessary cofactors. Rather, the genome contains many amino acid proteases, peptidases, and phosphotranferase transporters and hence requires amino acids and peptides that come from its environment. In addition, genome sequencing has revealed that L. johnsonii contains all of the genes necessary for the synthesis of pyrimidines, but lacks genes necessary for the synthesis of purines. Thus, L. johnsonni also must depend on its environment in order to acquire purine nucleotides. Since this organism must obtain amino acids and purine nucleotides from exogenous sources, it is thought that it relies on its human host or other intestinal microorganisms in order to obtain such monomeric nutrients (2).
Cell structure and metabolism
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Ecology
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Pathology
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Application to Biotechnology
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Current Research
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References
Edited by student of Rachel Larsen and Kit Pogliano
