ABSTRACT
Bacteria use a chemical language to communicate with each other which enables them to synchronize gene expression as a result of cell density. This special language which is called quorum sensing [QS] is based on producing and sensing the small signals and eventually leads them to perceive when a minimum population unit is reached. On the contrary, quorum sensing blockade [quorum quenching] has been recently grabbed scientists attention as a promising tool in controlling bacterial pathogens which utilize N-acyl homoserine lactone [AHL] to regulate their virulence factor production. Biodegradation of AHL molecules is an efficient way in QS interrupting which normally happens in the natural environment. In this survey, the effect of Bacillus cereus UT26 strain as an efficient quorum quencher on degrading both signal molecules [C4-HSL and 3oxoC12-HSL] of Pseudomonas aeruginosa was investigated. The strain strongly degraded both AHLs and hereby inhibited pyocyanin production in the lab condition. Moreover, co-culture experiments revealed that quorum quenching activity has an important role in interaction between different bacterial species; since the wild type [wt] strain of B. cereus UT26 reached 1000 fold higher growth yield comparing aiiA mutant strain of which has lost quorum quenching activity by a site directed mutation in AiiA lactonase gene
ABSTRACT
Saprophitic Pseudomonas species are root-colonizing bacteria that can improve plant health. Efficient exploitation of these bacteria in agriculture requires knowledge of traits that enhance ecological performance in the rhizosphere. Some Pseudomonas fluorescens strains present biocontrol properties, protecting the roots of some plant species against plant pathogens. These bacteria induce systemic resistance in the host plant, so it can better resist attack by a true pathogen. The bacteria outcompete other [pathogenic] soil microbes, e.g., by siderophores, giving a competitive advantage at scavenging for iron. The bacteria produce compounds antagonistic to other soil microbes, such as phenazine - type antibiotics or hydrogen cyanide. In this study the changes in the protein profile of P. fluorescens strain UTPF68, involved in the multiple interactions between plant [tomato] and an antagonistic agent [Trichoderma atroviride strain P1] investigated. Two-dimensional electrophoresis was used to analyze separately collected proteins from each one, two or three partner interactions. The results about differential produced spots in Pseudomonas proteome in each collation, showed that 18 differential spots became visible as new, 16 spots were absent, 17 spots were up-regulated and 1 spot was down-regulated, when Tomato-Pseudomonas [TP] condition was compared with control Pseudomonas alone [P]. Also more than 84 differential spots were accumulated in proteome of Pseuodomonas due to the presence of Trichoderma, as new, absent, increased and decreased spots. By comparison of conditions revealed 2 protein spots that detected by MS, have newly expressed in present of Plant and Trichoderma. These proteins corresponded to arginine deiminase of P. putida GB-1 and Chaperonin GroEL protein of P. putida S16 that their expressions associated to stress condition.The results indicated that the presence of Plant and Trichoderma induces major changes in the protein profile of Pseudomonas