Competition Triggers Plasmid-Mediated Enhancement of Substrate Utilisation in Pseudomonas putida

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 KanR 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

Entrapment of lipase in polymer of polyvinyl alcohol-boric acid for esterification in organic media

368-372Polyvinyl alcohol (PVA)-boric acid method has been utilized for entrapment of Candida rugosa lipase. Immobilized lipase was used to produce ethyl butyrate, a flavour ester showing 80.2% conversion in 72 h. Lipase in PVA-boric acid beads possessed the ability to synthesize variety of esters and was stable in various organic solvents with varying log P value from 2 to 8 under incubation at 50°C for 1 h.The immobilized lipase showed nearly full retention of activity even after 8 cycles of use, the activity then gradually decreased reaching to 56% conversion efficiency after 20 cycles and possesses a shelf-life of 10 months. The thermostability of the lipase increased three times upon immobilization. The immobilized enzyme possessed 40% higher activity compared to its free counterpart

Student assessment of teaching effectiveness of “bundle of changes”-A paired, controlled trial

Background : Inching toward optimum patient safety by training personnel is the prime aim of the ongoing medical education. Aims : To assess whether lectures targeted to improve quality care in ICU could improve ICU practitioners′ knowledge levels and to evaluate the effectiveness of teaching. Settings and Design : In this paired controlled trial, 50 ICU practitioners, i.e., anesthesia and medicine residents and nursing staff of our hospital attended a series of four lectures. Materials and Methods : Participants enrolled in the study attended lectures on "bundles of changes" in ICU, namely, introduction, ventilator bundle, central line bundle, and catheter-related blood stream infections and severe sepsis bundle. They were given a questionnaire of 15 multiple choice questions prior to and after the lectures. We evaluated their immediate knowledge acquisition and retention recall. Subsequently, they evaluated the effectiveness of the teaching programme by a questionnaire of 10 multiple choice questions. Statistical analysis used: Data for statistical analysis were tabulated and analyzed using SPSS-Pc 11.5 version software. Results : Fifty study participants completed all three questionnaires. There was an increase in the overall mean score in the post-lecture test (4.58 + 1.51 SD) (P < 0.001). Overall mean score increased significantly from 8.30 + 1.34 SD in THE pre-lecture test - to 12.02 + 1.61 SD in the postlecture re-test (3.72 + 1.39 SD) (P < 0.001). In the evaluation of teaching effectiveness 88% respondents agreed to most of the questions, signifying the effectiveness of the lectures. However, there were 10% who disagreed to the questions and only 2% strongly disagreed to all the questions. Conclusions : Teaching programmes such as the "bundle of changes" are effective in improving immediate knowledge acquisition and retention recall of the participants if designed keeping the target audience in mind

Protein as Chemical Cue: Non-Nutritional Growth Enhancement by Exogenous Protein in <i>Pseudomonas putida</i> KT2440

<div><p>Research pertaining to microbe-microbe and microbe-plant interactions has been largely limited to small molecules like quorum sensing chemicals. However, a few recent reports have indicated the role of complex molecules like proteins and polysaccharides in microbial communication. Here we demonstrate that exogenous proteins present in culture media can considerably accelerate the growth of <i>Pseudomonas putida</i> KT2440, even when such proteins are not internalized by the cells. The growth enhancement is observed when the exogenous protein is not used as a source of carbon or nitrogen. The data show non-specific nature of the protein inducing growth; growth enhancement was observed irrespective of the protein type. It is shown that growth enhancement is mediated via increased siderophore secretion in response to the exogenous protein, leading to better iron uptake. We highlight the ecological significance of the observation and hypothesize that exogenous proteins serve as chemical cues in the case of <i>P.putida</i> and are perceived as indicator of the presence of competitors in the environment. It is argued that enhanced siderophore secretion in response to exogenous protein helps <i>P.putida</i> establish numerical superiority over competitors by way of enhanced iron assimilation and quicker utilization of aromatic substrates.</p></div

BSA accelerates aromatic substrate utilization by inducing siderophore secretion.

<p><b>a</b>) Influence of BSA on various aromatic substrate utilization (<b>BA</b>: benzyl Alcohol, <b>Benzo</b>; Benzoate, <b>3MB</b>; 3-Methyl benzoate). <b>b</b>) Influence of exogenously added BSA and Fe⁺³ on growth of mutant (<i>P.putida</i>, ΔPpsD) on benzyl alcohol as sole carbon source.</p

Effect of BSA on growth of <i>P.putida</i>.

<p><b>a</b>) Effect of BSAaddition (0.5%) on growth of <i>P.putida</i> in complete media as well as in media devoid of either carbon source (glucose) or nitrogen source (ammonia). <b>b</b>) Residual concentration of BSA in supernatant at different time intervals. Concentration was determined using HPLC (mean±SD). <b>c</b>) HPLC chromatogram overlay showing identical peak area of BSA at different time intervals (BSA concentration 0.05% and 0.5%, w/v).</p

Effect of exogenous proteins (extracted from granular sludge) on growth of <i>P.putida</i> (mean±SD).

<p>Effect of exogenous proteins (extracted from granular sludge) on growth of <i>P.putida</i> (mean±SD).</p

Influence of different concentrations of BSA on growth rate of <i>P.putida</i> (mean±SD).

<p>Influence of different concentrations of BSA on growth rate of <i>P.putida</i> (mean±SD).</p