Lactobacillus johnsonii: Difference between revisions

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==Cell structure and metabolism==
==Cell structure and metabolism==
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
 
The cell surface of L. johnsonni contains various types of cell-surface proteins which are important in helping the microorganism attach to the mucosal surfaces of the GI tract. In addition, these cell-surface proteins can play a role in stimulating immune cells and can thus be one of the mechanistic explanations underlying L. johnsonii’s probiotic property of immunomodulation. Examples of these cell-surface proteins include mucus-binding proteins, glyosylated fimbriae, and an IgA protease (2).
 
As an anaerobic, lactic acid producing bacteria, L. johnsonii obtains its energy by fermenting disaccharides and hexoses to lactic acid. Specifically, the sugars it uses as substrates include galactose, maltose, sorbose/sorbitol, gentiobiose, isoprimerevose, isomaltose, and panose (2). L. johnosnii’s ability to undergo fermentation and thus produce lactic acid makes it a widely used microorganism in the industrial fermentation of dairy, meat, and vegetable products (3). However, as mentioned above, L. johnsonii lacks the biosynthetic pathways necessary for the generation of essential nutrients such as amino acids, purine nucleotides, and cofactors. Because of this, the genes which code for transporters in this microorganism are highly expressed and thus L. johnsonii contains a great number of certain transporters that are less frequent in other microorganisms. Specifically, it contains an abundance of AA-permease transporters and phosphotransferase (PTS)-type transporters. In addition, this microorganism has numerous various proteinases, peptide tranporters and peptidases in order to acquire nutrients from exogenous sources (2).


==Ecology==
==Ecology==

Revision as of 01:39, 5 June 2007

A Microbial Biorealm page on the genus Lactobacillus johnsonii

Classification

Higher order taxa

Bacteria; Firmicutes; Bacilli; Lactobacillales; Lactobacillaceae; Lactobacillus

Species

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

The cell surface of L. johnsonni contains various types of cell-surface proteins which are important in helping the microorganism attach to the mucosal surfaces of the GI tract. In addition, these cell-surface proteins can play a role in stimulating immune cells and can thus be one of the mechanistic explanations underlying L. johnsonii’s probiotic property of immunomodulation. Examples of these cell-surface proteins include mucus-binding proteins, glyosylated fimbriae, and an IgA protease (2).

As an anaerobic, lactic acid producing bacteria, L. johnsonii obtains its energy by fermenting disaccharides and hexoses to lactic acid. Specifically, the sugars it uses as substrates include galactose, maltose, sorbose/sorbitol, gentiobiose, isoprimerevose, isomaltose, and panose (2). L. johnosnii’s ability to undergo fermentation and thus produce lactic acid makes it a widely used microorganism in the industrial fermentation of dairy, meat, and vegetable products (3). However, as mentioned above, L. johnsonii lacks the biosynthetic pathways necessary for the generation of essential nutrients such as amino acids, purine nucleotides, and cofactors. Because of this, the genes which code for transporters in this microorganism are highly expressed and thus L. johnsonii contains a great number of certain transporters that are less frequent in other microorganisms. Specifically, it contains an abundance of AA-permease transporters and phosphotransferase (PTS)-type transporters. In addition, this microorganism has numerous various proteinases, peptide tranporters and peptidases in order to acquire nutrients from exogenous sources (2).

Ecology

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

Pathology

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

Application to Biotechnology

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

Current Research

Enter summaries of the most recent research here--at least three required

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by student of Rachel Larsen and Kit Pogliano