Vulnerability of Pathogenic Biofilms to Micavibrio aeruginosavorus

Abstract

The host specificity of the gram-negative exoparasitic predatory bacterium Micavibrio aeruginosavorus was examined. M. aeruginosavorus preyed on Pseudomonas aeruginosa, as previously reported, as well as Burkholderia cepacia, Klebsiella pneumoniae, and numerous clinical isolates of these species. In a static assay, a reduction in biofilm biomass was observed as early as 3 hours after exposure to M. aeruginosavorus, and an ϳ100-fold reduction in biofilm cell viability was detected following a 24-h exposure to the predator. We observed that an initial titer of Micavibrio as low as 10 PFU/well or a time of exposure to the predator as short as 30 min was sufficient to reduce a P. aeruginosa biofilm. The ability of Micavibrio to reduce an existing biofilm was confirmed by scanning electron microscopy. In static and flow cell experiments, M. aeruginosavorus was able to modify the overall P. aeruginosa biofilm structure and markedly decreased the viability of P. aeruginosa. The altered biofilm structure was likely caused by an increase in cell-cell interactions brought about by the presence of the predator or active predation. We also conducted a screen to identify genes important for P. aeruginosaMicavibrio interaction, but no candidates were isolated among the ϳ10,000 mutants tested.Biofilms are dense aggregations of microbial cells attached to a surface (9, 11). These surface-attached communities are known to have a significant impact on human health when they form on medical and surgical implants (4,13,16,18,34,36,40). A major difficulty in controlling surface-attached bacteria is their enhanced resistance to antimicrobial agents. Biofilms can be 10 to 1,000 times more resistant to antimicrobial agents than their planktonic counterparts (5,20,26,27,35). The difficulty in controlling biofilms by conventional antibiotic therapy led researchers to examine other methods of biofilm control. Among these alternative techniques is the use of biological control agents, including invertebrates, protozoa, and bacteriophages (10,14,15,19,21,28,29,33,38,43,45,46). Predatory prokaryotes from the genus Bdellovibrio have also been shown to have potential for biofilm control (17,22).In 1982, while searching for Bdellovibrio samples in wastewater, Lambina and colleagues isolated a new species of exoparasitic bdellovibrio-like bacteria that they called Micavibrio (24). Like Bdellovibrio spp., Micavibrio spp. are characterized by an obligatory parasitic life cycle. Micavibrio organisms are gram negative, small (ϳ0.5 to 1.5 m long), rod shaped, and curved and have a single polar flagellum. Phylogenetic analyses have placed Micavibrio spp. within the ␣ subgroup of proteobacteria (12). The Micavibrio cycle of development includes the following stages: motile Micavibrio organisms attach to the cell surfaces of host bacteria, followed by growth of the exoparasite on the surface of the host and, finally, death of the infected cells (2, 25). Unlike Bdellovibrio, Micavibrio spp. were shown to have a high degree of host specificity; for exampl...

Review on biofilm formation and its control options

“…Similarly, in Pseudomonas aeruginosa, depolymerase enzyme reduced the viscosity of alginates and the EPS of the organism, thereby leading to dispersal of biofilm.The dual approach of impregnation of medical devices with phages and incorporation of phages in hydrogel coating of catheter has proven its efficacy, especially in Staphylococcus epidermidis (Del Pozo et al, 2007). The vulnerability of pathogenic biofilms to Micavibrio aeruginosavorus and Bdellovibrio bacteriovorus attack has been documented (Kadouri et al, 2007). However, recent studies have shown the dispersal of films by using genetically engineered bacteriophages (Lu and Collins, 2007).…”

Invasion and Survival of Salmonella in the Environment: The Role of Biofilms

“…They are gram negative, small curved rod shaped (0.5 x 1.5 mm), bacteria with a single polar flagellum. A titer as low as 10 plaque forming units per well of M. aeruginosavorus was sufficient to produce a 78% reduction in a P. aeruginosa biofilm after 30 min exposure in a static assay (Kadouri et al, 2007). Dopheide et al (2011) examined the grazing interactions of two ciliates, the free-swimming filter feeder Tetrahymena spp.…”

Pinpointing the Origin of Mitochondria

“…Micavibrio, on the other hand, feed by "leeching" externally to the surface of the prey cell and therefore has an epibiotic lifestyle (Lambina, et al 1983;Davidov, et al 2006;Kadouri, et al 2007;Dashiff, et al 2010).…”

“…Micavibrio usually exhibit a high degree of prey specificity. For example, M. aeruginosavorus was initially reported to prey only on Pseudomonas aeruginosa, Burkholderia cepacia and Klebsiella pneumoniae (Lambina, et al 1983;Kadouri, et al 2007). However a breach in prey specificity was recently demonstrated and M. aeruginosavorus was found to be able to prey on many other bacterial species including…”

“…In comparison, Micavibrio, members of the α-proteobacteria, have received much less attention, at least partly due to the difficulty to obtain axenic culture and partly due to the lack of good genetic tools to study them. In order to gain greater insights into its predatory lifestyle and to further understand the evolution of bacterial predation in general, we sequenced one of the better studied strains, Micavibrio aeruginosavorus ARL-13 (Davidov, et al 2006;Kadouri, et al 2007;Dashiff, et al 2010) and characterized its transcriptome during the attachment and attack stages of its growth cycle.…”