Microbes and Us - Essay Example

P. uminicola are Gram-negative non motile rods (0.8-1m by 0.8-30m). They are either pleomorphic or coccobacilli with slightly tapered and rounded ends (Hobson and Stewart, 15). Cells are usually encapsulated, arranged as singles or in pairs. Colonies on the surface of cultures appear smooth, entire, convex, opaque and light buff coloured. Deeply situated colonies are larger and lenticular (Bryant et al., 18). Electron microscopic observations show an accumulation of lightly stained carbohydrates in its cytoplasm (Lou et al., 1486).

P. ruminicola grows at 30-37°C and has a pH of 5.5. They are capable of utilizing diverse sources of carbon and nitrogen; and have an efficient energy metabolism (Hobson and Stewart, 15). The fermentation products in a glucose medium are succinic, formic and acetic acid (Bryant et al., 18).

They are generalists capable of degrading many carbohydrates except cellulose. Degradation of starch due to amylase activity converts starch into maltose and maltodextrins. The α-amylases break down the carbohydrate chain randomly.

Polysaccharides such as xylans and pectins present in plant cell walls are also degraded by carboxymethylcellulose and xylanase activity due to both extracellular and intracellular CM-cellulases and pectinases. The xylanase activity of the P. ruminicola has been attributed to multiple xylanase genes encoding endoglucanase, endo xylanase and oxygen-sensitive exoxylanase activity (Gasparic et al., 2958) while proteolytic ability is due to a unique dipeptidyl peptidase activity (DAP1) (Hobson and Stewart, 15). It helps overcome the lack of free transport of amino acids in the cell (Mackie & Morrison, 7).

Obligate anaerobes P. ruminicola are among the most abundant (19%) of the rumen and hindgut microbiota in cattle and sheep (Hobson and Stewart, 15). P. ruminicola is also an indigenous population of the human oral cavity and surface (Haraldsson, 23).

As a consequence of the symbiotic relationship of P. ruminicola along with other similar microbes with the ruminants, the latter can derive nutrition from the herbaceous materials made of starch and hemicelluloses.

Further due to the proteolytic activity of P. ruminicola low quality protein sources ingested by the host animal are converted into high-quality microbial cell proteins that are then made available to the host animal.

P. ruminicola is also used for the prevention of rumen acidosis, a significant disease of ruminants, also responsible for lower milk production by cattle (RAGFAR, 2007).

One major disadvantage of the microbe is the discovery of the enzyme β-glucosidase that catalyzes the step leading to the release of cyanide from cyanogenic plant glycosides (Wulffs-Strobel & Wilson, 5884).

P. internmedia are capable of degrading hemolysins, adhesions and hemaglutinins and also produce tissue-degrading enzymes. P. ruminicola is being studied to counteract this pathogen (Haraldsson, 23).

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