Carnobacterium
Classification
Domain: Bacteria
Phylum: Firmicutes
Class: Bacilli
Order: Lactobacillales
Family: Carnobacteriaceae
Species
Carnobacterium alterfunditum
Carnobacterium divergens
Carnobacterium funditum
Carnobacterium gallinarum
Carnobacterium iners
Carnobacterium inhibens
Carnobacterium jeotgali
Carnobacterium maltaromaticum
Carnobacterium piscicola
Carnobacterium mobile
Carnobacterium pleistocenium
Carnobacterium viridans
- Please note this is not an exhaustive list.
Description and Significance
Carnobacterium are gram-positive rod-shaped lactic acid bacteria. Although they are lactic acid producing bacteria, they grow in a PH range of 7-9. Most of the species produce lactic acid through the fermentation of carbohydrates such as glucose. The presence of Carnobacterium can be found in seawater as well as dairy, fish, & meat products. They are commonly found in in polar regions and temperate environments due to their tolerance to freezing temperatures and thawing. Such examples include the psycrophilic anaerobic species C. maltaromaticum, C. divergens & C. pleistocenium. They also are tolerant of high pressure conditions. Recently, a piezophilic strain was isolated from s trench at a depth of 2500 meters. Certain species have preservative qualities of meat products; however there is also evidence that suggests others attribute to meat spoilage when improperly stored. C. pleistocenium has been found in a permafrost fox tunnel in Alaska. The ice dates back to the Pleistocene Epoch era which is around 11,000 years ago.
Genome Structure
Carnobacterium have linear For C. divergens and C. pleistocenium, the genome size was estimated to 3.2 Mb, and for C. alterfunditum, it was estimated to be 2.9 Mb (Daniel, 1995; Pikuta et al., 2005) We only found record of one Carnobacterium genome sequencing project completed for the Carnobacterium sp. AT7. The data already available indicate that the C. AT7 genome contains 2.4 Mb and encodes 2388 proteins. The final sequence of the Carnobacterium species comprised one chromosome of 2,635,294 bp and one plasmid of 50,105 bp. The chromosome contained a G+C ration of around 35.25%. This chromosome was comprised of 2,420 predicted protein-encoding genes, 67 tRNA genes, 8 rRNA operons, and 1 single 5S rRNA gene. The plasmid contained a G+C content of 31.53% which housed 54 protein-encoding genes. (http://www.genomesonline.org) (Liolios et al., 2006).
Rachman C, Kabadjova P, Valcheva R, Prévost H & Dousset X (2004) Identification of Carnobacterium species by restriction fragment length polymorphism of the 16S–23S rRNA gene intergenic spacer region and species-specific PCR. Appl Environ Microbiol 70: 4468–4477.
Cell Structure, Metabolism and Life Cycle
These microorganisms are thin, rod shaped and found in singles rods or in small chains. They are gram stain positive, meaning they have a large amount of peptidoglycan in their cell walls. They can be motile or non-motile and do not have spores. The only species proven to be mobile are C. mobile, C. alterfunditum and C. funditum. Carnobacterium generally produce lactic acid mainly from glucose fermentaion. However, C. pleistocenium also produce CO2, ethanol, and acetic acid as well. Most species are psychrophilic and psychrotolerant, meaning they are able to grow and reproduce at temperatures between -10 to 20 °C. There is little known about the metabolism of Carnobacterium, except that they produce lactic acid and get their energy from fermentation of different hexoses. Acetic acid and ethanol are also common byproducts. They grow extremely well when heme, a blood pigment with iron, is added to aerobic conditions. However, they can also live in anaerobic conditions as well making them facultive anaerobes. Some interesting finding are that C. maltaromaticum and C. mobile may produce gas from glucose. Also, as a bi-product of a few Carnobacterium specie's fermentation, volatile alcohols, ketones, and hydrocarbons tend to accumulate in their environment. Their environment in this case is typically the inside of a fishes intestine. However, Further studies need to be conducted to determine the positive and negative effects of these metabolites.
Ecology and Pathogenesis
Carnobacterium spp. appear to have both the temperate and polar aquatic environments as habitats including live fish, marine sponges, and Arctic sea water as well as the deep sea. C. maltaromaticum and C. divergens have been isolated from tropical fish products, including smoked surubim, a Brazilian tropical freshwater fish, and from vacuum-packed tuna caught in the Indian Ocean. The presence of carnobacteria has also been documented in the terrestrial environment, including Canadian winter soil and permafrost ice. In these harsh conditions, Carnobacterium possess trials that play a large role in their survival. A cold-active β-galactosidase from C. maltaromaticum and a cold-adapted alanine dehydrogenase from a Carnobacterium species related to C. alterfunditum have been found that enhance the Carnobacterium's ability to grow at low temperatures. An example is the isolation of a Carnobacterium sp. preserved in a permafrost ice wedge for 25,000 years. Some carnobacterial isolates are derived from natural high-pressure habitats, as seen in deep Artic water. They are also relatively resistant to high-pressure processing and are found in high concentrations in vacuum-packed and chilled squid mantle and cold-smoked salmon. In order to vacuum-pack a fish for preservation, it is treated with 200–400 MPa for 15–20 minutes. There is no research of Carnobacterium causing disease. However, they have been as protective cultures that pathogenic and spoilage microorganisms. Also, C. divergens and C. maltaromaticum are commonly found in the spoilage of chilled seafood and meat products after it has left frozen storage and improperly stored in ice. On the other hand, C. maltaromaticum has been FDA approved for use as a preservative in meats when the meats are properly stored.
References
Benson DA, Karsch-Mizrachi I, Lipman DJ, Ostell J, Sayers EW (2009). GenBank. Nucleic Acids Res. 2009 Jan;37(Database issue):D26-31. Epub 2008 Oct 21. [PubMed]
Sayers EW, Barrett T, Benson DA, Bryant SH, Canese K, Chetvernin V, Church DM, DiCuccio M, Edgar R, Federhen S, Feolo M, Geer LY, Helmberg W, Kapustin Y, Landsman D, Lipman DJ, Madden TL, Maglott DR, Miller V, Mizrachi I, Ostell J, Pruitt KD, Schuler GD, Sequeira E, Sherry ST, Shumway M, Sirotkin K, Souvorov A, Starchenko G, Tatusova TA, Wagner L, Yaschenko E, Ye J (2009). Database resources of the National Center for Biotechnology Information. Nucleic Acids Res. 2009 Jan;37(Database issue):D5-15. Epub 2008 Oct 21. [PubMed]
Wallbanks, S., A. J. Martinez-Murcia, J. L. Fryer, B. A. Phillips, and M. D. Collins.(1990). "16S RRNA Sequence Determination for Members of the Genus Carnobacterium and Related Lactic Acid Bacteria and Description of Vagococcus Salmoninarum Sp. Nov." International Journal of Systematic Bacteriology 40.3: 224-30
Voget, S., B. Klippel, R. Daniel, and G. Antranikian. "Complete Genome Sequence of Carnobacterium Sp. 17-4. (2011)" Journal of Bacteriology 193.13 :3403-404
Author
Page authored by Heather Moule and Catherine Hencsie, student of Dr. Walker & Dr. Kashefi at Michigan State University.
