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Competition triggers plasmid-mediated enhancement of substrate utilisation in Pseudomonas putida.

Joshi H, Dave R, Venugopalan VP - PLoS ONE (2009)

Bottom Line: Inert microspheres mimicking competitor cell size and concentration did not elicit any significant induction, further suggesting the role of physical cell-cell interaction.We conclude that P. putida harbouring pWW0 experience a competitive stress when grown as dual-species consortium, irrespective of the counterpart being BA degrader or not.The immediate effect of this stress is a marked increase in expression of TOL, leading to rapid utilization of the available carbon source and massive increase in its population density.

View Article: PubMed Central - PubMed

Affiliation: Biofouling and Biofilm Processes Section, Water and Steam Chemistry Division, BARC Facilities, Kalpakkam, India.

ABSTRACT
Competition between species plays a central role in the activity and structure of communities. Stable co-existence of diverse organisms in communities is thought to be fostered by individual tradeoffs and optimization of competitive strategies along resource gradients. Outside the laboratory, microbes exist as multispecies consortia, continuously interacting with one another and the environment. Survival and proliferation of a particular species is governed by its competitive fitness. Therefore, bacteria must be able to continuously sense their immediate environs for presence of competitors and prevailing conditions. Here we present results of our investigations on a novel competition sensing mechanism in the rhizosphere-inhabiting Pseudomonas putida KT2440, harbouring gfpmut3b-modified Kan(R) TOL plasmid. We monitored benzyl alcohol (BA) degradation rate, along with GFP expression profiling in mono species and dual species cultures. Interestingly, enhanced plasmid expression (monitored using GFP expression) and consequent BA degradation were observed in dual species consortia, irrespective of whether the competitor was a BA degrader (Pseudomonas aeruginosa) or a non-degrader (E. coli). Attempts at elucidation of the mechanistic aspects of induction indicated the role of physical interaction, but not of any diffusible compounds emanating from the competitors. This contention is supported by the observation that greater induction took place in presence of increasing number of competitors. Inert microspheres mimicking competitor cell size and concentration did not elicit any significant induction, further suggesting the role of physical cell-cell interaction. Furthermore, it was also established that cell wall compromised competitor had minimal induction capability. We conclude that P. putida harbouring pWW0 experience a competitive stress when grown as dual-species consortium, irrespective of the counterpart being BA degrader or not. The immediate effect of this stress is a marked increase in expression of TOL, leading to rapid utilization of the available carbon source and massive increase in its population density. The plausible mechanisms behind the phenomenon are hypothesised and practical implications are indicated and discussed.

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Time course of BA degradation by PP9, PAO1 and PP9+PA01.PP9 and PAO1 (106 cells each) and PP9+PA01 (106+106) were inoculated in Tris+BA medium and incubated at 100 rpm and 30°C. Samples were withdrawn at regular time intervals and the residual BA was estimated by HPLC.
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pone-0006065-g001: Time course of BA degradation by PP9, PAO1 and PP9+PA01.PP9 and PAO1 (106 cells each) and PP9+PA01 (106+106) were inoculated in Tris+BA medium and incubated at 100 rpm and 30°C. Samples were withdrawn at regular time intervals and the residual BA was estimated by HPLC.

Mentions: Comparative analysis of time course of benzyl alcohol (BA) utilization by Pseudomonas putida KT2440 (termed PP9) and Pseudomonas aeruginosa (PAO1) was done using monospecies and two-species cultures. Both the species are BA degraders. About 106 cells each of PP9 and PAO1 were inoculated separately in shake flasks containing 100 ml Tris minimal media containing 5 mM BA as the sole carbon source. Samples were drawn at different intervals and analyzed for residual BA. As shown in Figure 1, PP9 utilized 50% of BA in 30 h; the organism completely utilized BA in 36 h, whereas PAO1 utilized 50% BA in 48 h. In order to find out how the two organisms, both having the ability to utilize the same carbon source, do when cultured together, we inoculated 106cells each of PAO1 and PP9 together in 100 ml Tris BA medium. The time-course of BA utilization by the dual-species consortium is shown in Figure 1. BA was utilised to the extent of 50% in 17 h and completely in less than 24 h of incubation. A significant reduction in the shoulder indicated that the degradation started earlier than in the previous case (PP9 alone), with reduced induction time.


Competition triggers plasmid-mediated enhancement of substrate utilisation in Pseudomonas putida.

Joshi H, Dave R, Venugopalan VP - PLoS ONE (2009)

Time course of BA degradation by PP9, PAO1 and PP9+PA01.PP9 and PAO1 (106 cells each) and PP9+PA01 (106+106) were inoculated in Tris+BA medium and incubated at 100 rpm and 30°C. Samples were withdrawn at regular time intervals and the residual BA was estimated by HPLC.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2698150&req=5

pone-0006065-g001: Time course of BA degradation by PP9, PAO1 and PP9+PA01.PP9 and PAO1 (106 cells each) and PP9+PA01 (106+106) were inoculated in Tris+BA medium and incubated at 100 rpm and 30°C. Samples were withdrawn at regular time intervals and the residual BA was estimated by HPLC.
Mentions: Comparative analysis of time course of benzyl alcohol (BA) utilization by Pseudomonas putida KT2440 (termed PP9) and Pseudomonas aeruginosa (PAO1) was done using monospecies and two-species cultures. Both the species are BA degraders. About 106 cells each of PP9 and PAO1 were inoculated separately in shake flasks containing 100 ml Tris minimal media containing 5 mM BA as the sole carbon source. Samples were drawn at different intervals and analyzed for residual BA. As shown in Figure 1, PP9 utilized 50% of BA in 30 h; the organism completely utilized BA in 36 h, whereas PAO1 utilized 50% BA in 48 h. In order to find out how the two organisms, both having the ability to utilize the same carbon source, do when cultured together, we inoculated 106cells each of PAO1 and PP9 together in 100 ml Tris BA medium. The time-course of BA utilization by the dual-species consortium is shown in Figure 1. BA was utilised to the extent of 50% in 17 h and completely in less than 24 h of incubation. A significant reduction in the shoulder indicated that the degradation started earlier than in the previous case (PP9 alone), with reduced induction time.

Bottom Line: Inert microspheres mimicking competitor cell size and concentration did not elicit any significant induction, further suggesting the role of physical cell-cell interaction.We conclude that P. putida harbouring pWW0 experience a competitive stress when grown as dual-species consortium, irrespective of the counterpart being BA degrader or not.The immediate effect of this stress is a marked increase in expression of TOL, leading to rapid utilization of the available carbon source and massive increase in its population density.

View Article: PubMed Central - PubMed

Affiliation: Biofouling and Biofilm Processes Section, Water and Steam Chemistry Division, BARC Facilities, Kalpakkam, India.

ABSTRACT
Competition between species plays a central role in the activity and structure of communities. Stable co-existence of diverse organisms in communities is thought to be fostered by individual tradeoffs and optimization of competitive strategies along resource gradients. Outside the laboratory, microbes exist as multispecies consortia, continuously interacting with one another and the environment. Survival and proliferation of a particular species is governed by its competitive fitness. Therefore, bacteria must be able to continuously sense their immediate environs for presence of competitors and prevailing conditions. Here we present results of our investigations on a novel competition sensing mechanism in the rhizosphere-inhabiting Pseudomonas putida KT2440, harbouring gfpmut3b-modified Kan(R) TOL plasmid. We monitored benzyl alcohol (BA) degradation rate, along with GFP expression profiling in mono species and dual species cultures. Interestingly, enhanced plasmid expression (monitored using GFP expression) and consequent BA degradation were observed in dual species consortia, irrespective of whether the competitor was a BA degrader (Pseudomonas aeruginosa) or a non-degrader (E. coli). Attempts at elucidation of the mechanistic aspects of induction indicated the role of physical interaction, but not of any diffusible compounds emanating from the competitors. This contention is supported by the observation that greater induction took place in presence of increasing number of competitors. Inert microspheres mimicking competitor cell size and concentration did not elicit any significant induction, further suggesting the role of physical cell-cell interaction. Furthermore, it was also established that cell wall compromised competitor had minimal induction capability. We conclude that P. putida harbouring pWW0 experience a competitive stress when grown as dual-species consortium, irrespective of the counterpart being BA degrader or not. The immediate effect of this stress is a marked increase in expression of TOL, leading to rapid utilization of the available carbon source and massive increase in its population density. The plausible mechanisms behind the phenomenon are hypothesised and practical implications are indicated and discussed.

Show MeSH