Importance of Bdellovibrio

Bdellovibrio have a dramatic effect on the population of their prey bacteria. Though some projections have been as small as 40%, it has been estimated that up to 80% of the bacteria in a given marine environment are susceptable to infection by this predatory bacteria (Rice et al, 1998). The broad prey spectra includes the common genera of Aeromonas, Escherichia, Pseudomonas, Salmonella and Vibrio (Pan et al, 1997). It is a controversial topic, but they may be a major factor in bacterial mortality in the aquatic environment and responsible for as much cell death as viruses.

Cyanobacterial blooms are often a major problem in both euthrophic lakes and reservoirs, and can have quite a devestating effect in a quick amount of time. There is a growing body of evidence that shows bacteria, such as Bdellovibrio, that act as predatory agents in fresh and marine water environments help to limit the growth during this phenomenon. By artificially introducing these predators we may be able to safely and effectively control bloom formations. As biological control agents they are selective for nuisance species, and also have the obvious advantage of being completely natural. In a recent study, several blooms in Japan where sprayed with a sample of predatory bacteria, and these blooms were found to be completely lysed within 60 hours of treatment (Rashidan et al, 2001).

Though they do not occur in the same high concentrations as viruses, Bdellovibrio still has a great effect on bacterial numbers as it has such a wide range of hosts. It is only able to target Gram-negative bacteria, however, and there are varying degrees of susceptability amongst species; some species, such as Vibrio, appear to be much more vulnerable than others (Rice et al, 1998). Since prey concentrations must be at least 1x10ex4 cells per mL for growth, low concentrations of the prey are not greatly affected by predation, as Bdellovibrio numbers drop below this minimum level. In fact, predation rates are directly linked to prey concentration, with higher predation rates and greater impact being correlated to high prey abundance. It is due to these predator-prey dynamics that Bdellovibrio, and other predatory bacteria, have been labelled modulators of growth, rather than eradicators (Rice et al, 1998).

Other aspects of the genus that make it significant is the ability to reduce pathogenic and spoilage-causing bacteria in food products, but this concept is relatively new and still being researched (see Food Preservation). For research, Bdellovibrio makes an excellent model organism for predator-prey interaction, host-recognition, regulation of simple development patterns and cell-signalling (Gray et al, 1991).