Brevibacterium

Brevibacterium, like most other coryneforms, occur in the Actinobacteria phylum, the Actinomycetales order but occurs in the Micrococcinae suborder along with other coryneform genera such as Arthrobacter (Funke et. al 1996; McGraw-Hill, 2005). They are Gram-positive bacteria which also demonstrate pleomorphism, aerobic respiration, non-fermentation and have a high GC content of 70% (Gruner, 1993; Brock 2009; Bergeys, 1984). Such properties do make them a perfect example of coryneform bacteria. However, their habitat, pathogenicity etc. do differ from other members of the group.

Figure 1.1 - Shows the colony morphology of Brevibacterium linens. Note the v-shapped/clubbed cells that are a key characteristic of all coryneform bacteria. (Source: Microbewiki, 2012)

Habitat

Brevibacterium species such as B. casei & B. epidermidis, showing halotrophic properties, colonise the human skin as part of the microflora (Bergeys, 1984). However, a number of species such as B. Casei also occur in cheese curd and can metabolise casein and milk (Bergeys, 1984). Other species such as B. lines are used commercially to ripen cheeses due to their proteolytic activity and occur in Camembert and Brick cheese varities (Bergeys, 1984). They also produce the characteristic red colour found on such cheeses as Limburger (Figure 1.2) (Bergeys, 1984).

Other varieties such as B. marinum, B. celere occur in the marine habitat with B. celere being extracted from the thallus of brown algae (Bergeys, 1984; Ivanova et al., 2004). Again other species such as B. ammoniilyticum occur in the sludge of waste water (K. Srinivasan, 2012).

Figure 1.2 - Displays the key redish outer layer produced on cheeses like Limburger by bacteria such as B. linens.

Pathogenicity

A number of species of Brevibacterium have been classed as pathogenic. Species such as B. casei have caused endocarditis (Meier, 1981). In addition the genus has been known to case peritoneal dialysis, corneal ulcers, speticimia and osteomyelitis (Bergeys, 1984). Therefore it is evident that Brevibacterium can act as key opportunistic pathogens.