Classification Bacteria; Firmicutes; Bacilli; Lactobacillales; Lactobacillaceae
Species Pediococcus pentosaceus
Description and significance Pediococcus pentosaceus are coccus shaped microbes, Gram-positive, non-motile, non-spore forming, and are categorized as a “lactic acid bacteria” . Pediococcus pentosaceus are categorized as a “lactic acid bacteria” because the end product of its metabolism is lactic acid . Pediococcus pentosaceus like most lactic acid bacteria are anaerobic and ferment sugars. Since the end product of metabolism is a kind of acid, Pediococcus pentosaceus are acid tolerant. They can be found in plant materials, ripened cheese, and a variety of processed meats. Pediococcus pentosaceus is industrially important due to its ability as a starter culture to ferment foods such as various meats, vegetables, and cheeses. Pediococcus pentosaceus bacteria is being cultured and researched for its ability to produce an antimicrobial agent (bacteriocins) as well its use in food preservation . Pediococcus pentosaceus can be cultured at 350C – 400C but are unable to grow at 500C . Pediococcus pentosaceus are able to grow in pH values between 4.5 and 8.0. The bacteria grows more stably at the more acidic pH range . Pediococcus are unique in that they form tetrads. These tetrads are formed “via cell division in two perpendicular directions in a single plane ”
Genome structure The genome has been sequenced is made up of 1832387 nucleotides organized in a circular manner . The genome has 1755 protein encoding genes and 72 RNA genes . The genome has a 37.4% GC content. There are three to five resident plasmids. The plasmids give P. pentosaceus the ability to metabolize different compounds. Pediococcus pentosaceus are related to other lactic acid bacteria. In a comparison of ribosomal proteins Pediococcus pentosaceus are related to Lactobacillus brevis and Lactobacillus plantarum.
Cell structure and metabolism Pediococcus pentosaceus are Gram-positive microbes that produce energy via fermentation . P. pentosaceus are anaerobic like most lactic acid producing bacteria . Anaerobic microbes do not use oxygen as an electron acceptor for metabolism. Fermentation is the breakdown of ATP to establish a membrane ion gradient. Lactic acid is the by product of anaerobic fermentation for Pediococcus pentosaceus. P. pentosaceus transforms hexose sugars such as glucose . Pediococcus pentosaceus processes “hexose sugars via the Embden-Meyerhof pathway” . The Embden-Meyerhof pathway is also known as glycolysis. Pediococcus pentosaceus are able to process glucose using the enzyme glucose dehydrogenase . Glucose dehydrogenase needs nicotinamide adenine dinucleotide phosphate (NADP) as a cofactor . NADP serves as an electron transporter. Some lactic acid bacteria are able to degrade proteins as a nitrogen source, but it has not been determined whether or not Pediococcus pentosaceus utilizes this pathway .
Ecology P. pentosaceus can produce an antimicrobial agent known as bacteriocins  “against several species of Lactobacillus, lactococcus, leuconostoc, pediococcus, staphylococcus, enterococcus, bacillus and listeria” . Antimicrobial agents are produced by bacteria to limit the growth of competitors and/or other harmful bacteria. The bacteriocin isolated in Pediococcus pentosaceus was labeled pediocin P. . The end product of fermentation is lactic acid which lowers the environmental pH.
Pathology No known diseases are caused by Pediococcus pentosaceus.
Application of Biotechnology The bacteriocin produced by Pediococcus pentosaceus can be used to as a food preservative. The bacteriocins only inhibit Gram-positive microbes . Gram-negative bacteria were not inhibited. Pediocin P. inhibited several species of food pathogens such as Listeria monocytogenes which can cause Listeriosis .
Current Research Most of the current research is associated with Pediococcus pentosaceus application of biotechnology. The plasmids are still being sequenced in order to improve food preservation methods . P. pentosaceus is part of the DOE Joint Genome Institution projects to complete the genome sequence which will use the information to enhance lactic acid production to be used in industry . Continuing research is still being done to refine Pediococcus pentosaceus as a starter culture for fermentation . In China, scientists are trying to develop a mixed starter culture using P. pentosaceus in order to preserve fresh water silver carp instead of using salt . These starter cultures are a necessary step in processing meats. These scientists want to ferment the freshwater fish in order to reduce salt consumption. Food preservation improvements have been a major focus because of Pediococcus pentosaceus ability to produce bacteriocin. Food fermentation is a low cost method of food preservation. Pediococcus pentosaceus genome was recently compared to other lactic acid bacteria . It was determined through ribosomal proteins that Pediococcus pentosaceus falls into the family Lactobacillaceae . This research helped create a phylogenetic tree of Lactobacillales .
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