Lactobacillus paracasei (commonly abbreviated as L. paracasei) is a gram-positive, facultatively heterofermentative species of lactic acid bacteria that are commonly used in dairy product fermentation and probiotics. L. paracasei is a bacterium that operates by commensalism. It is commonly found in many human habitats such as our intestinal tracts and mouths as well as sewages, silages, and previously mentioned dairy products. The name includes morphology, a rod-shaped (bacillus shape) bacterium with a width of 2.0 to 4.0μm and length of 0.8 to 1.0μm.
So far, thirty four different strains of L. paracasei have been isolated from a variety of environments. Sixteen of those strains have been isolated from dairy, ten from plants, and eight from human and animal gastrointestinal tracts. L. paracasei is genotypically and phenotypically indistinguishable from other members of its genus such as Lactobacillus casei and Lactobacillus rhamnosus. However, they are easily differentiated from each other by their fermentation profiles. Its fermentative properties allows it to be used as biological food processors and supplements for diets and medical disorders, especially in the gastrointestinal tract.
Lactobacillus paracasei is a gram-positive, facultatively heterofermentative, non-spore forming microorganism. The cells of L. paracasei are typically rod shaped, with a size range of 2.0μm to 4.0μm in width, and 0.8 to 1.0μm in length. The organism is nonmotile. L. Paracasei cells often have square ends, and may exist either in single form or in chains.
L. paracasei grows optimally at in a temperature range between 10 and 37 °C. No growth takes place above 40 °C. The organism is able to survive for approximately 40 seconds in a maximum temperature of 72 °C. As L. Paracasei is facultatively heterofermentative: lactic acid is produced from most strains.
L. paracasei exist as a common inhabitant of the human gastrointestinal tract as part of the normal flora. Naturally fermented vegetables, milk, and meat may also contain strains of L. paracasei.
Lactobacillus paracasei belongs to kingdom Bacteria. L. paracasei is part of the division Firmicutes, and also belongs to the class Bacilli. The order and family are Lactobacillales and Lactobacillaceae respectively. The argument on the nomenclature of L. paracasei versus L. casei has been one of intense debate. Most of the species profiled as L. casei or L. paracasei have been found to be part of the same species. In 1989, it was proposed that L. paracasei be designated a subspecies (paracasei) to account for the species that it shares DNA homology with. It has been shown their names have been used interchangeably in scientific literature. 16S RNA sequence homology has confirmed the relatedness between these species.
Historically, the difference between Lactobacillus paracasei and other lactobacilli has been based on biochemical characteristics. There is an approximately 90% sequence identity between casei, paracasei, and rhamnosus. However, there are some differential criteria that are commonly used to differentiate between them. These differential criteria include nutritional requirements and growth environment. L. Paracasei has been found to show specific differences with other Lactobacillus spp. in that it is somewhat heat resistant, grows well in ripening cheese, and it has high proteolytic activity.
L. paracasei has been found to have 34 strains. These strains have been isolated from various countries around the world. Although there is a small correlation between phylogenetic relatedness and origin of isolation, currently there is not enough evidence to support direct proof of the relationship.
L. paracasei's genome contains circular DNA and varies slightly among the different strains isolated. On average, the genomes are 2.9 to 3.0 millions of base pairs (commonly abbreviated Mb). It has a GC-content between 46.2 and 46.6% and is predicted to encode about 2800 to 3100 proteins. The difference in the genomes of these strains lies in variant cell envelopes, secretory proteins, and polysaccharides. Many of the commonly coded proteins are cell-surface associated cell-wall hydrolases that protect the cell against apoptosis. These enzymes have been shown to provide cellular protection to human epithelial cells.
Genetic diversity for the different L. paracasei genomes was assessed using multilocus sequence typing (MLST) and amplified fragment length polymorphism (AFLP). MLST is a technique used for classifying microbes by the use of DNA fragments from essential genes of the organism. AFLP is a Polymerase Chain Reaction (PCR) tool used in DNA profiling to amplify a desired DNA fragment with the use of restriction enzymes and ligands.
Role in Science and Medicine
L. paracasei has a pronounced role within science and medicine. Probiotics also known as helpful bacteria have risen to popularity within the health community over the years. The idea of probiotics is that a balance between healthy and unhealthy microbes in the normal flora of the gastrointestinal tract leads to health benefits. Lactobacillus paracasei has been identified as one of the bacterial species in the probiotic group. The organism has been used in studies to prove a correlation between its implementation and health benefits. L. paracasei is a part of the normal human gut microbiota. When the gastrointestinal mucosa of healthy humans is analyzed, L. paracasei is often found. The most well studied strains of L. paracasei for health benefits are: IMPC2.1 and 8700:2.
L. paracasei IMPC2.1 was studied to analyze its potential as a chemoprophylactic in gastrointestinal cells. In this context a chemoprophylactic is defined as a drug that fights disease, with an emphasis on infections. The study found that gastrointestinal cells were susceptible to apoptosis and cell growth from both heat-killed and viable IMPC2.1 strains. This study provided positive evidence for future study into the use of IMPC2.1 as a chemoprophylactic.
L. paracasei 8700:2 is studied after being isolated from healthy human gastrointestinal mucosa The strain was selected for analysis based on its potential to be re-isolated from human feces. This is important, because the foundation of the probiotic theory is that a bacterium may survive passing through the gastrointestinal tract. In addition to its probiotic potential, strain 8700:2 was also found to exhibit strong opposition against Salmonella enterica and Heliobacter pylori, two pathogens commonly found in the gastrointestinal tract. Lastly, 8700:2 was found to break down oligofructose and inulin, while also growing rapidly on both and producing lactic acid as the end product.
LAB (Lactic Acid Bacteria) were classified and grouped in the early 1900s after gaining scientists' attention after observing the bacteria's interactions in different foods, especially dairy products. In 1991, Martinus Beijerinck, a Dutch microbiologist, separated Lactobacillus as gram positive bacteria from the previously known LAB group. L. paracasei has been recently classified as a part of the Lactobacillus casei group of probiotics. However, it has no clear taxonomic position. The name L. paracasei was proposed for rejection in 1996 by Dicks, Duplessis, Dellaglio, and Lauer.
- Orlando, A.; Refolo, M. G.; Messa, C.; Amati, L.; Lavermicocca, P.; Guerra, V.; Russo, F. (October 2012). "Antiproliferative and Proapoptotic Effects of Viable or Heat-Killed IMPC2.1 and GG in HGC-27 Gastric and DLD-1 Colon Cell Lines". Nutrition and Cancer 64 (7): 1103–1111. doi:10.1080/01635581.2012.717676.
- Smokvina, Tamara; Wels, Michiel; Polka, Justyna; Chervaux, Christian; Brisse, Sylvain; Boekhorst, Jos; Vlieg, Johan E. T. van Hylckama; Siezen, Roland J.; Highlander, Sarah K. (19 July 2013). "Lactobacillus paracasei Comparative Genomics: Towards Species Pan-Genome Definition and Exploitation of Diversity". PLoS ONE 8 (7): e68731. doi:10.1371/journal.pone.0068731.
- COLLINS, M. D.; PHILLIPS, B. A.; ZANONI, P. (1 April 1989). "Deoxyribonucleic Acid Homology Studies of Lactobacillus casei, Lactobacillus paracasei sp. nov., subsp. paracasei and subsp. tolerans, and Lactobacillus rhamnosus sp. nov., comb. nov.". International Journal of Systematic Bacteriology 39 (2): 105–108. doi:10.1099/00207713-39-2-105.
- Ward, L. J. H.; Timmins, M. J. (August 1999). "Differentiation of Lactobacillus casei, Lactobacillus paracasei and Lactobacillus rhamnosus by polymerase chain reaction". Letters in Applied Microbiology 29 (2): 90–92. doi:10.1046/j.1365-2672.1999.00586.x.
- Felten, A; Barreau, C; Bizet, C; Lagrange, PH; Philippon, A (Mar 1999). "Lactobacillus species identification, H2O2 production, and antibiotic resistance and correlation with human clinical status.". Journal of clinical microbiology 37 (3): 729–33. PMID 9986841.
- HESSLE; HANSON,; WOLD, (May 1999). "Lactobacilli from human gastrointestinal mucosa are strong stimulators of IL-12 production". Clinical and Experimental Immunology 116 (2): 276–282. doi:10.1046/j.1365-2249.1999.00885.x.
- Rogan, WJ; Gladen, BC; Hung, KL; Koong, SL; Shih, LY; Taylor, JS; Wu, YC; Yang, D; Ragan, NB; Hsu, CC (Jul 15, 1988). "Congenital poisoning by polychlorinated biphenyls and their contaminants in Taiwan.". Science 241 (4863): 334–6. PMID 3133768. doi:10.1126/science.3133768.
- Molin, G.; Jeppsson, B.; Johansson, M.-L.; Ahrné, S.; Nobaek, S.; Ståhl, M.; Bengmark, S. (March 1993). "Numerical taxonomy of Lactobacillus spp. associated with healthy and diseased mucosa of the human intestines". Journal of Applied Bacteriology 74 (3): 314–323. PMID 8468264. doi:10.1111/j.1365-2672.1993.tb03031.x.
- Maiden, Martin; Jane Bygraves; Edward Feil (January 6, 1998). "Multilocus sequence typing: A portable approach to the identification of clones within populations of pathogenic microorganisms". Proceedings of the National Academy of Sciences of the United States of America. 6 95: 3140–3145. PMC 19708. PMID 9501229. doi:10.1073/pnas.95.6.3140. Retrieved February 26, 2014.
- Kumar, Awanish; Anuradha Dube (February 2013). "Amplified fragment length polymorphism: an adept technique for genome mapping, genetic differentiation, and intraspecific variation in protozoan parasites [electronic resource].". 2 112. pp. 457–466.
- Goldin, Barry R.; Gorbach, Sherwood L. (1992). "Probiotics for humans". pp. 355–376. doi:10.1007/978-94-011-2364-8_13.
- Makras, L.; Van Acker, G.; De Vuyst, L. (3 November 2005). "Lactobacillus paracasei subsp. paracasei 8700:2 Degrades Inulin-Type Fructans Exhibiting Different Degrees of Polymerization". Applied and Environmental Microbiology 71 (11): 6531–6537. doi:10.1128/AEM.71.11.6531-6537.2005.
- Bernstein, Charles N; Nugent, Zoann; Blanchard, James F (15 March 2011). "5-Aminosalicylate Is Not Chemoprophylactic for Colorectal Cancer in IBD: A Population Based Study". The American Journal of Gastroenterology 106 (4): 731–736. doi:10.1038/ajg.2011.50.
- Stiles, ME; Holzapfel, WH (Apr 29, 1997). "Lactic acid bacteria of foods and their current taxonomy.". International Journal of Food Microbiology 36 (1): 1–29. PMID 9168311. doi:10.1016/s0168-1605(96)01233-0.