Cannibalisme bactérien : le renouveau ?

Abstract

Predatory bacteria : rebirth ? The discovery of predatory bacteria is recent. These lytic bacteria, mainly incurved rods (d-proteobacteria) prey upon Gram-negative rods and justify some hope as alternative to antibiotics. A lot of publications has given details on the genus Bdellovibrio and the species, Bdellovibrio bacteriovorus, tiny and incurved Gram-negative rod, motile, aerobic and obligatory predation of a host. Its spectrum of action was directed among various Gram-negative rods pathogens for humans and animals : enterobacteria, various species of Pseudomonas, vibrios... Such bacteria were isolated from several ecosystems : soil, waters from rivers, estuaries and mammal stools. The lytic cycle (3-4 hours) was individualized including steps : attachment, penetration into periplasmic space with a burst size of 3-6 cells, and liberation (lysis). Finally the absence of multiplication on cell cultures combined to low inflammatory in animals conducted to use such bacteria as alternative. Nevertheless the discoveries of broad-spectrum antibiotics limited further research on cannibalism. Fortunately the emergence of multiresistant bacteria to antibiotics highlighted the rebirth of predatory bacteria. Other publications gave details on taxonomy of new genera (Bacteriolyticum, Bacteriovorax, Halobacteriovorax, Peredibacter, Variovorax), on genomes varying from 2.97 to 3.85 Md, equivalent between 3100 and 3800 genes coding for enzymes for anaerobic respiration, partial hydrolysis of peptidoglycan (glycanase, peptidases), and numerous proteases, nucleases, low toxicity of LPS. Such characteristics justified perspectives as agent of biocontrol by accurate individualization of in vitro spectrum in wound, ocular, gingival and broncho-pulmonary infections. The effects of B. bacteriovorus on well-being and Salmonella colonization were detailed in chickens and cattle. Bdellovibrio has various applications in food industry as control in blight for soybean, modulators of vibrios in seawater, oysters and shrimps. Finally Bdellovibrio and like organisms (BALOs) are effective at reducing through predation the population of harmful bacteria, support for its potential use as a probiotic. Nevertheless we need more investigations particularly in medical field.