Microbial signaling

Secondary Messenger
The ubiquitous bacterial secondary messenger c-di-GMP controls exopolysaccharide synthesis, flagella- and pili-based motility, biofilm formation, gene expression and interactions of bacteria with eukaryotic hosts. Most of the identities of c-di-GMP receptors and end targets have remained unknown.

Regulatory network of morA signalling in Pseudomonas aeruginosa.

Pseudomonas aeruginosais a well-known nosocomial and opportunistic human pathogen, widely considered as the main cause for increased morbidity and mortality in cystic fibrosis (CF) patients. It causes persistent, antibiotic-resistant infection of the respiratory tract by forming biofilms and uses type-III secretion system (TTSS) to inject virulence determinants directly into host cells. morA has been observed to control biofilm formation in Pseudomonas aeruginosa PAO1 without affecting growth rate or cell size.

Gene regulatory analysis was carried out based on expression profiling of morA-POA1 mutants and wildtype (WT) planctonic cells. Regulatory networks have been generated using an in-house networking program, based on promoter motif similarities and showed up-regulation of virulence regulators. Hence, we are interested in studying the effect of MorA on secreted virulence factors using genetic and proteomic platforms.

Structure and function of di-guanylate cyclase

The GGDEF domain contains a conserved GG(D/E)EF sequence motif and is coupled in a modular fashion with different sensory input or information transfer domains. The GGDEF domain is a diguanylate cyclase (DGC), which catalyzes the synthesis of c-di-GMP from two molecules of GTP. Therefore, GGDEF domains are proposed to represent the output of a complex bacterial signal transduction network which converts signals from different cellular compartments into the production of a secondary messenger, cdi-GMP.

Cellular localization of GGDEF and EAL proteins by GFP tagging.

Previous work has shown that morA contains both GGDEF and EAL domains and localizes to the bacterial pole.


Signaling/Bacteria Mortility

Affymetrix:

This is the first microarray platform that we had performed and the chips that we used were Arabidopsis ATH1 Genome Array Genechip (for Arabidopsis Thaliana) and P. aeruginosa Genome Array Genechip (for Pseudomonas aeruginosa).

Combimatrix

We performed our Pseudomonas microarray using this platform (CustomArray 12K and 4 x 2K). We used this to establish hypothesis and we are currently work on few of the interesting features that were revealed by microarray analysis

Video microscopy analysis

ImagePro: We use the Image Pro software to analyse and compare the motility speeds of different Pseudomonas strains from the videos captured and to do quantification of the biofilm formed on slides.