Lactobacillus acidophilus

Classification

Higher order taxa

Bacteria; Firmicutes; Bacilli; Lactobacillales; Lactobacillaceae; Lactobacillus

Species

Lactobacillus acidophilus

NCBI: TaxonomyGenome

Strains

Laboratory: NCFM, 4962, CNRZ216, CNRZ218

Human: HA1, HA2, HA3, HM2, HM6

Pig: PA3, PA12, PA19, P18, P47

Chicken: C1, C2, C3, C7, C11

Description and significance

In general, Lactobacilli inhabit the gastrointestinal (GI) tract of humans and animals. Lactobacilli are considered to have a probiotic effect that contributes to overall health and well being.

Of the Lactobacillus species, L. acidophilus is the most well known and is commercially distributed as a probiotic. Early studies of L. acidophilus were performed on strains isolated from fecal material of humans, pigs and chickens. It has been characterized as a short gram-positive rod (2-10μm), homofermentative and optimal growth temperatures of 37˚C-42˚C.

Further isolation and investigation into the physiological, biochemical, genetic, and fermentative properties have been widely explored in both humans and animals. The L. acidophilus strain, NCFM, has been commercially available in the United States as a probiotic strain since the mid-1970s.

Genome structure

The complete circular genome of the NCFM strain of L. acidophilus contains 1,993,564 nucleotides. The DNA GC content was determined to be 34.71%. There are 1,7864 ORFs and 72.5% have been classified functionally.

L. acidophilus NCFM contains no plasmids.

Cell structure and metabolism

L. acidophilus grows in low pH and anaerobic conditions.

An acid induced ATPase was identified in L. acidophilus. Based on primary structure and the genetic organization, it was further classified as a F₁F₀-type ATPase. Its similarity to the streptococcal ATPase and the H⁺ inducibility of the operon suggests that it is responsible for an ATP-dependent exclusion of protons in order to maintain cytoplasmic pH.

Pathology

The exact mechanism of the probiotic effect is still under investigation.

One mechanism is based on competition for space in the GI tract. L. acidophilus has the ability to form a strong adherence to the GI tract which inhibits the adherence of other potentially harmful microbes.

References

Altermann, E., Russell, W.M., Azcarate-Peril, M.A., et al. "Complete genome sequence of the probiotic lactic acid bacterium Lactobacillus acidophilus NCFM". Proceedings of the National Academy of Sciences of the United States. 2005. Volume 102. No. 11.

Sanders, M.E., Klaenhammer, T.R. "The Scientific Basis ofLactobacillus acidophilus NCFM Functionally as a Probiotic". Journal of Dairy Sciences. 2001. Volume 84. Pages 319-331.

Gilliland, S.E., Speck M.L. and Morgan, C.G. "The Detection of Lactobacillus acidophilus in Feces of Humans, Pigs and Chickens". Applied Microbiology. October 1975. Pages 541-545.

Edited by Jennifer B. Samore, student of Rachel Larsen and Kit Pogliano