Regulation of parasitism by host density: The Bdellovibrio-Rhizobium interrelationship

Keya, S. O.; Alexander, Martin

doi:10.1016/0038-0717(75)90044-9

Cited by 42 publications

(21 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this work, we did not observe a marked difference between the abilities of Micavibrio to attack P. aeruginosa cells as biofilms and as freefloating cells. This outcome could be explained by the inability of the predator to completely eradicate its planktonic prey, as previously demonstrated for bdellovibrios (23). Another explanation may be that under the conditions tested, biofilm formation does not enhance the ability of P. aeruginosa to withstand predation compared to that of planktonic cells.…”

Section: Discussionmentioning

confidence: 53%

Vulnerability of Pathogenic Biofilms to Micavibrio aeruginosavorus

Kadouri

Venzon

O’Toole

2007

Appl Environ Microbiol

View full text Add to dashboard Cite

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...

show abstract

Section: Discussionmentioning

confidence: 53%

Vulnerability of Pathogenic Biofilms to Micavibrio aeruginosavorus

Kadouri

Venzon

O’Toole

2007

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…2). Interestingly, under the experimental conditions typically used to assess bdellovibrio predation, it is widely reported that bdellovibrios never completely eradicate their planktonic prey (19,45). The low volume and/or the high host-predator ratio in our static system may explain why no planktonic cells were detected after predation.…”

Section: Discussionmentioning

confidence: 89%

“…It is believed that biofilms might offer good conditions for bdellovibrios' survival since these organisms have been found in natural marine biofilms but are not always recovered from the surrounding water (17,18,48). It is suggested that in a biofilm bdellovibrios can benefit from higher prey density, which has been shown to be necessary for Bdellovibrio survival (19,44).…”

mentioning

confidence: 99%

Susceptibility of Biofilms to Bdellovibrio bacteriovorus Attack

Kadouri

O’Toole

2005

Appl Environ Microbiol

190

164

View full text Add to dashboard Cite

Biofilms are communities of microorganisms attached to a surface, and the growth of these surface attached communities is thought to provide microorganisms with protection against a range of biotic and abiotic agents. The capability of the gram-negative predatory bacterium Bdellovibrio bacteriovorus to control and reduce an existing Escherichia coli biofilm was evaluated in a static assay. A reduction in biofilm biomass was observed as early as 3 h after exposure to the predator, and an 87% reduction in crystal violet staining corresponding to a 4-log reduction in biofilm cell viability was seen after a 24-h exposure period. We observed that an initial titer of Bdellovibrio as low as 10 2 PFU/well or an exposure to the predator as short as 30 min is sufficient to reduce a preformed biofilm. The ability of B. bacteriovorus to reduce an existing biofilm was confirmed by scanning electron microscopy. The reduction in biofilm biomass obtained after the first 24 h of exposure to the predator remained unchanged even after longer exposure periods and reinoculation of the samples with fresh Bdellovibrio; however, no genetically stable resistant population of the host bacteria could be detected. Our data suggest that growth in a biofilm does not prevent predation by Bdellovibrio but allows a level of survival from attack greater than that observed for planktonic cells. In flow cell experiments B. bacteriovorus was able to decrease the biomass of both E. coli and Pseudomonas fluorescens biofilms as determined by phase-contrast and epifluorescence microscopy.

show abstract

“…Various authors have reported that a minimal prey density of approximately 10 5 -10 6 CFU per gram or milliliter of environmental sample is required to maintain efficient elimination by freshwater/terrestrial BALOs (Keya and Alexander, 1975;Uematsu, 1980). The survival of BALOs could be maintained in continuous culture when the prey density is as low as 10 4 CFU mL À1 (Varon et al, 1984).…”

Section: Discussionmentioning

confidence: 99%