![]() ![]() In this scenario, different prey species select for distinct populations of Bacteriovorax OTUs, and thereby influence the presence, distribution and services of the predators in nature. Salinity and temperature are among such parameters ( Williams and Falkler, 1984 Pineiro et al., 2007) and there is speculation on a role for the prey ( Sutton and Besant, 1994 Pineiro et al., 2004). Such findings have advanced knowledge of Bacteriovorax, and raised new questions about environmental parameters that account for the varied distribution patterns of different OTUs. ![]() This has made possible geographical distribution studies that have found that some OTUs occur widely and in diverse environments whereas, others are restricted to certain ecosystems ( Pineiro et al., 2007). One approach, comparative analysis of 16S rRNA sequences, has enabled identification and detection of specific Bacteriovorax phylogenetic clusters or operational taxonomic units (OTUs) within populations ( Pineiro et al., 2004). Therefore, few methods are available for distinguishing between BALO isolates. As obligate predators, the growth of wild-type Bacteriovorax and other BALOs requires co-cultivation with a prey bacterium, which negates their characterization by the many cultural methods that demand pure cultures. The Bacteriovorax are in the BALO group and are ubiquitous in salt–water environments ( Pineiro et al., 2008). The latter phase begins when, following attack, the predator penetrates through the prey cell's outer membrane into its periplasmic space where it grows, multiplies and lyses the prey ( Rendulic et al., 2004) ( Figure 1). ![]() The predatory cycle of BALOs is unique in being biphasic with an extracellular ‘hunt’ phase, in which the organisms search for and attack its prey, and an intracellular phase. Contrary to the higher forms where predation and multiplication are not directly linked, the bacterial prey for the BALOs not only serves as a food source but also a growth and multiplication chamber. Among the obligate predatory bacteria, the most studied are several genera known collectively as the Bdellovibrio and like organisms (BALOs), which prey on many Gram negative bacteria ( Guerrero et al., 1986 Schoeffield and Williams, 1990 Jurkevitch et al., 2000). Of the microorganisms, viral and protistan predation have received greatest attention ( Wildschutte et al., 2004 Jurkevitch, 2007 Danovaro et al., 2008). Predation has been studied extensively among animals ( Sinclair et al., 2003 Finke and Denno, 2004) however, in the microbial world it has not been well investigated ( Jurkevitch, 2007). The results of this study have revealed impacts of the prey on Bacteriovorax predation and in structuring the predator community, and advanced understanding of predation behavior in the microbial world. This initiative should provide a basis for further efforts to characterize the predatory patterns of bacterial predators. Therefore, we proposed a designation of versatilist for this predator. Not only did Bacteriovorax Cluster IX exhibit the versatility to be the exclusive efficient predator on Vibrio vulnificus, thereby, behaving as a specialist, but was also able to prey with similar efficiency on Vibrio parahaemolyticus, indicative of a generalist. The results of laboratory experiments confirmed the differential predation of Bacteriovorax phylotypes on the two bacteria species. The two prey species yielded distinct Bacteriovorax populations, evidence that selective pressures shaped the predator community and diversity. In this study, Bacteriovorax, a predator within the group of BALOs, in environmental waters were fed two prey bacteria, Vibrio vulnificus and Vibrio parahaemolyticus. However, selective pressures among prey and predatory bacteria have been rarely investigated. In the macroscopical world, both predator and prey influence the population size of the other's community, and may have a role in selection. Among the bacteria, the most studied obligate predators are the Bdellovibrio and like organisms (BALOs) that prey on many other bacteria. Although predator–prey interactions among higher organisms have been studied extensively, only few examples are known for microbes other than protists and viruses. ![]()
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