Overview

Brief Summary

Prevotella strains are Gram-negative, non-motile, singular cells that thrive in anaerobic growth conditions. They are generally host associated and most species exist as obligate anaerobes (Finegold, 1996). Prevotella species are present in humans, often existing in the oral cavity, gastrointestinal tract, and vagina (Avguštin et al., 2001). In humans, they can act as an opportunistic pathogen, causing periodontal and tooth problems such as gingivitis and periodontitis (Finegold, 1996).

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Physical Description

Morphology

Species of the Prevotella genus are generally bacillus to almost coccoid bacteria (Finegold, 1996). They are pleomorphic, taking on different forms during life cycle, and do not form endospores (Bacteroides and Prevotella Infections, 2009). Prevotella melaninogenica and P. asaccharolytica form gram-negative rods that are dark brown, due to a heme derivative (Finegold, 1996). Prevotella intermedia can communicate to form biofilms within their habitat that are often composed of mixed species.

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Ecology

Habitat

Prevotella species are often present on most mucosal surfaces, existing in the oral cavity, gastrointestinal tract, and female genital tract (Avguštin et al., 2001). Prevotella species thrive on tissues with decreased oxidation-reduction potentials, such as those with limited blood supply or tissue necrosis (Finegold, 1996). Growth of Prevotella intermedia favors a slightly basic pH with a temperature held between 34-36˚C (Marcotte and Lavoie, 1998). Additionally, increased hormone production, such as that during adolescence and pregnancy, has been shown to contribute Prevotella proliferation (Kornman and Loesche, 2006).

It has also been determined that abundance of Prevotella in the GI tract is greater in persons with diets rich in carbohydrates (Enserink, 2011). In the gastrointestinal tract, the dominant commensal taxa of Prevotellaceae and Bacteroides compete to occupy niches within the community. In contrast, Prevotella species in the oral cavity frequently exist in a complementary habitat with other taxa, such as Treponema (Faust et al., 2012). Prevotella is also found in great abundance in the gastrointestinal tract of cows and sheep, playing an integral role in carbohydrate digestion (Bacteroides and Prevotella Infections, 2009).

Prevotella melaninogenic and Prevotella oralis are common flora present in the mouth. Prevotella melaninogenic illustrates selective localization, often found in the gingival crevice but not other surfaces of the oral cavity (Finegold, 1996).

In a quanitative study of the female genital tract, it was found that half of the participants had Bacteroides and Prevotella species present. Common species of Prevotella isolated from healthy women included: P. oralis, P. bivia, P. disiens, P. oris, and P. buccae (Finegold, 1996).

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Associations

Prevotella species exist as commensal bacteria in the environment. In the oral cavity, P. intermedia exist in a commensal environment with species of Actinomyces, Streptococci, Veillonella, as well as with many other species (Kolenbrander et al., 2002). These species have developed cell-cell recognition, as well as having undergone genetic and metabolite exchange (Kolenbrander et al., 2002). It is believed that the signaling molecule, autoinducer-2, produced by P. intermedia is used to facilitate communication between oral bacteria (Kolenbrander et al., 2002). Prevoltella intermedia has also been shown to cooperate with Peptostreptococcus micros, enhancing the virulence factor of micros when creating dentoalveolar infections (Kolenbrander et al., 2002). Prevotella also play an integral role in carbohydrate digestion of some grazing animals, being one of the most numerous microbes found in the rumen and hind gut of cattle and sheep (Avguštin et al., 2001).

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Diseases and Parasites

Several Prevotella species act as opportunistic pathogens, often penetrating tissues and establishing an infection at mucosal surfaces (Finegold, 1996). There are currently about twenty known species of the genus Prevotella that are known to cause infection. Prevotella can form abscesses and genital tract infections (Finegold, 1996). Depleted reduction-oxidation potential within tissues can contribute to infection (Finegold, 1996).

Prevotella are known to cause diseases in humans. Prevotella intermedia is a periodontal pathogen that has been linked to inflammation of the gums and the related disease of gingivitis (Dorn et al., 1998). The extensive proliferation of Prevotella intermedia along with other anaerobic bacteria in the oral cavity has also been associated with periodontitis (Dorn et al., 1998). Periodontitis is the detachment of connective tissue along the alveolar bone and is usually preceded by gingivitis (Dorn et al., 1998). It results in tooth separation, movement, and swelling of the gums. Subsequent internalization of Prevotella intermedia from periodontal pockets is hypothesized to be strain specific, being limited to those that possess specific receptors for fimbriae (Dorn et al., 1998). Additionally, there is a correlation between coronary heart disease and periodontal disease that may be linked to the invasion of artery smooth muscle and artery endothelial cells by Prevotella intermedia (Dorn et al., 1998).

Species of Prevotella can also cause chronic sinusitis, chronic otitis media, cervical adenitis, retropharyngeal space infection, aspiration pneumonia, lung abscess and necrotizing pneumonia (Bacteroides and Prevotella Infections, 2009). Risk of infection by Prevotella is facilitated by a decrease in the redox potential of tissues, and can be best prevented through increased oxidation (Finegold, 1996).

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Life History and Behavior

Behavior

Members of this genus are non-motile and act as opportunistic pathogens (BioProject, 2012).

--- How do abiotic (pH, temperature, nutrients) environments affect Prevotella species?

Growth of Prevotella intermedia favors a slightly basic pH with a temperature held between 34-36˚C (Marcotte and Lavoie, 1998). Additionally, increased hormone production, such as that during adolescence and pregnancy, has been shown to contribute Prevotella proliferation (Kornman and Loesche, 2006).

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Evolution and Systematics

Evolution

Prevotella were formerly classified under Bacteroides malninogenicus. Prevotella species have recently been reclassified into two groups: Prevotella melaninogenica and Prevotella intermedia (Bacteroides Infection, 2011). Prevotella belong to the phylogenetic division of Cytophaga-Flexibacter-Bacteroides (CFB) (Avguštin et al., 2001). This is an ecologically diverse group consisting of many bacteria related by only a few species (Avguštin et al., 2001). Additionally, species of Prevotella can be categorized as both “ruminal” and “non-ruminal,” with species in the same category often exhibiting a closer genetic resemblence (Avguštin et al., 2001). In August of 2007, two strains of novel species were added to the genus Prevotella based on 16S rRNA gene sequences and phylogenetic analysis (Ueki et al., 2007). These two strains, KB7(T) and A42, were the first species of the genus known to exist in a natural habitat, independent of a mammalian host (Ueki et al., 2007).

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Physiology and Cell Biology

Physiology

Prevotella are generally obligate anaerobes with a fermentive form of metabolism (Finegold, 1996). Some species, such as P. melaninogenica, require both vitamin K and heme to function (Finegold, 1996). Additionally, the Prevotella genus has been associated with β-Lactamase activity, partially accounting for the resistance to some β-lactam antibiotics (Finegold, 1996).

Species of Prevotella are known to produce the following enzymes: collagenase, neuraminidase, deoxyribonuclease, haparinase, and proteases (Fingeold, 1996). In the oral cavity, P. intermedia secretes salivary IgA proteases that break down IgA1 and IgA2, which facilitates proliferation of P. intermedia and subsequent diseases such as gingivitis and periodontitis (Marcotte and Lavoie, 1998).

Some Prevotella are resistant to β-lactam antibiotics, including penicillins and cephalosporins (Finegold, 1996). These species include Prevotella that possess a β-lactamase inhibitor, such as pigmented Prevotella (Bacteroides Infection, 2011). Effective antiobiotic treatments for Prevotella include: metronidazole, amoxycillin/clavulanate, ureidopenicilins, carbapenems, cephalosporins, clindamycin and chloramphenicol (Bacteroides Infection, 2011). Treatment with some antibiotics, including aminoglycosides, trimethoprim/sulfamethoxazole, and quinolones, can contribute to the proliferation of Prevotella species (Finegold, 1996).

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Molecular Biology and Genetics

Molecular Biology

Eleven Prevotella genomes are available via the Broad Institute (Prevotella Group, 2012).

  • P. buccae (Oral Taxon 560 D17)
    • Size: 3.36 Mb
    • GC Content (%): 50.95
    • Number of Genes: 2,617
  • P. melaninogenica (Oral Taxon 469 D18)
    • Size: 3.29 Mb
    • GC Content (%): 40.86
    • Number of Genes: 2,461
  • Prevotella sp. F0039
    • Size: 2.48 Mb
    • GC Content (%): 37.50
    • Number of Genes: 1,976
  • Prevotella sp. (Oral Taxon 317 F0108)
    • Size: 4.1 Mb
    • GC Content (%): 47.05
    • Number of Genes: 2,926
  • P. oris C735
    • Size: 3.35 Mb
    • GC Content (%): 43.91
    • Number of Genes: 2,742
  • Prevotella sp. F0323
    • Size: 2.59 Mb
    • GC Content (%): 45.49
    • Number of Genes: 2,014
  • P. histicola F0411
    • Size: 2.99 Mb
    • GC Content (%): 41.18
    • Number of Genes: 2,479
  • P. oulorum F0390
    • Size: 2.81 Mb
    • GC Content (%): 46.78
    • Number of Genes: 2,488
  • Prevotella sp. C561
    • Size: 4.03 Mb
    • GC Content (%): 41.83
    • Number of Genes: 3,402
  • P. maculosa F0099
    • Size: 3.15 Mb
    • GC Content (%): 47.71
    • Number of Genes: 2,574
  • P. micans F0438
    • Size: 2.49 Mb
    • GC Content (%): 45.51
    • Number of Genes: 2,064
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Relevance to Humans and Ecosystems

Benefits

A number of diverse applications have been suggested for Prevotella. One such application tested the efficacy of a Prevotella bryantii probiotic for cows suffering from subacute ruminal acidosis. It was determined that P. bryantii applications increased fat content in the milk, however the probiotic had no impact on the pH of the rumen (Chiquette et al., 2012). The role of the changing microbiome associated with lactation and breast-feeding is also currently being studied. The presence of Prevotella species has been shown to increase 1-6 months after birth, suggesting a possible role in the infant microbiome and presenting the opportunity for potential probiotic production (Cabrera-Rubio et al., 2012).

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Wikipedia

Prevotella

Prevotella is a genus of Gram-negative bacteria.

Bacteroides melaninogenicus has been reclassified and split into Prevotella melaninogenica and Prevotella intermedia.[1]

Prevotella spp. are members of the oral and vaginal flora, and are recovered from anaerobic infections of the respiratory tract. These infections include aspiration pneumonia, lung abscess, pulmonary empyema, and chronic otitis media and sinusitis. They have been isolated from abscesses and burns in the vicinity of the mouth, bites, paronychia, urinary tract infection, brain abscesses, osteomyelitis, and bacteremia associated with upper respiratory tract infections. Prevotella spp. predominate in periodontal disease and periodontal abscesses. [2]

In a study of gut bacteria of children in Burkina Faso (in Africa), Prevotella made up 53% of the gut bacteria, but were absent in age-matched European children.[3] Studies also indicate that long-term diet is strongly associated with the gut microbiome composition—those who eat plenty of protein and animal fats typical of Western diet have predominantly Bacteroides bacteria, while for those who consume more carbohydrates, especially fibre, the Prevotella species dominate.[4]

P. copri is possibly connected to rheumatoid arthritis.[5]

A recent study on Prevotella derived from humans compared the gene repertoires of its species derived from different body sites of human. It also reported an open pan- genome showing vast diversity of gene pool. [6]

Species[edit]

References[edit]

  1. ^ "Bacteroides Infection: Overview - eMedicine". Retrieved 2008-12-11. 
  2. ^ Tanaka S, Yoshida M, Murakami Y et al. (2008). "The relationship of Prevotella intermedia, Prevotella nigrescens and Prevotella melaninogenica in the supragingival plaque of children, caries and oral malodor". J Clin Pediatr Dent 32 (3): 195–200. PMID 18524268. 
  3. ^ De Filippo, C.; Cavalieri, D.; Di Paola, M.; Ramazzotti, M.; Poullet, J. B.; Massart, S.; Collini, S.; Pieraccini, G.; Lionetti, P. (2010). "Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa". Proceedings of the National Academy of Sciences 107 (33): 14691–6. doi:10.1073/pnas.1005963107. PMC 2930426. PMID 20679230. 
  4. ^ Wu GD, Chen J, Hoffmann C, Bittinger K, Chen YY, Keilbaugh SA, Bewtra M, Knights D, Walters WA, Knight R, Sinha R, Gilroy E, Gupta K, Baldassano R, Nessel L, Li H, Bushman FD, Lewis JD (October 7, 2011). "Linking long-term dietary patterns with gut microbial enterotypes". Science 334 (6052): 105–8. doi:10.1126/science.1208344. PMC 3368382. PMID 21885731. 
  5. ^ Jose U Scher, Andrew Sczesnak, Randy S Longman, Nicola Segata, Carles Ubeda, Craig Bielski, Tim Rostron, Vincenzo Cerundolo, Eric G Pamer, Steven B Abramson, Curtis Huttenhower, Dan R Littman; Sczesnak; Longman; Segata; Ubeda; Bielski; Rostron; Cerundolo; Pamer; Abramson; Huttenhower; Littman (November 5, 2013). "Expansion of intestinal Prevotella copri correlates with enhanced susceptibility to arthritis". ELife 2: e01202. doi:10.7554/eLife.01202. PMC 3816614. PMID 24192039. 
  6. ^ Vinod Kumar Gupta, Narendrakumar M Chaudhari, Suchismitha Iskepalli, Chitra Dutta (March 5, 2015). "Divergences in gene repertoire among the reference Prevotella genomes derived from distinct body sites of human". BMC Genomics. 16:153. doi:10.1186/s12864-015-1350-6. PMC 4359502. 
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