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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.

Show MeSH
Time course of BA degradation by PP9 in presence of different bacteria.106 cells of PP9 were inoculated with similar number of Lactobacillus sp., Deinococcus radiodurans, P. aeruginosa PAO1 and E. coli JM 101. Samples were withdrawn at regular intervals and residual BA was estimated with HPLC.
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pone-0006065-g010: Time course of BA degradation by PP9 in presence of different bacteria.106 cells of PP9 were inoculated with similar number of Lactobacillus sp., Deinococcus radiodurans, P. aeruginosa PAO1 and E. coli JM 101. Samples were withdrawn at regular intervals and residual BA was estimated with HPLC.

Mentions: Lastly, to check whether enhanced BA utilization in PP9 is only induced in presence of PA01 and E. coli JM 101 or whether this phenomenon is more generalized and stands true for other bacterial species as well, we monitored BA degradation profile of PP9 in mixed cultures containing a Gram positive bacillus (Lactobacillus sp.) and a Gram negative coccus (Deinococcus radiodurans) (both are non BA degraders). The experiments were repeated with PP9 and the other two bacteria in the log ratio of 1∶1 each. As shown in Figure 10, BA degradation was found to be enhanced in all the cases where PP9 was co-cultured with another bacterial species. The results, thus, indicate that competition stress emanating from multiple sources can induce PP9 to enhance its TOL expression.


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 in presence of different bacteria.106 cells of PP9 were inoculated with similar number of Lactobacillus sp., Deinococcus radiodurans, P. aeruginosa PAO1 and E. coli JM 101. Samples were withdrawn at regular intervals and residual BA was estimated with HPLC.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0006065-g010: Time course of BA degradation by PP9 in presence of different bacteria.106 cells of PP9 were inoculated with similar number of Lactobacillus sp., Deinococcus radiodurans, P. aeruginosa PAO1 and E. coli JM 101. Samples were withdrawn at regular intervals and residual BA was estimated with HPLC.
Mentions: Lastly, to check whether enhanced BA utilization in PP9 is only induced in presence of PA01 and E. coli JM 101 or whether this phenomenon is more generalized and stands true for other bacterial species as well, we monitored BA degradation profile of PP9 in mixed cultures containing a Gram positive bacillus (Lactobacillus sp.) and a Gram negative coccus (Deinococcus radiodurans) (both are non BA degraders). The experiments were repeated with PP9 and the other two bacteria in the log ratio of 1∶1 each. As shown in Figure 10, BA degradation was found to be enhanced in all the cases where PP9 was co-cultured with another bacterial species. The results, thus, indicate that competition stress emanating from multiple sources can induce PP9 to enhance its TOL expression.

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