LAUSR

Signal Transduction Systems are essential for microorganisms to respond to their ever changing environment. It can be distinguished into one-component systems, two-component system, and extracytoplasmic-function σ factors. Abundances of a few signal-transducing proteins, termed herein as Sensory Proteins (SPs), have previously been reported to be correlated to the genome size and the ecological niche of the certain gram-positive bacteria. No such reports are available for gram-negative bacteria. The current study tries to investigate the relationship of the abundances of SPs to genome size in Escherichia coli, and the bacterial patho- or phylo-types. While the relationship between SP abundance and genome size could not be established, the 'Sensory Protein Index' (SPI), a new metric defined herein, was found to be correlated to E. coli virulence. In addition, significant association among the distribution of SPs and E. coli pathotypes were observed. Results indicated that such associations might be due to genomic re-arrangements to best utilize the resources available in a given ecological niche. Overall, the study provides an in-depth analysis of the occurrence of different SPs among pathogenic and non-pathogenic E. coli Possibilities of using the SPI as a marker of identifying pathogenic strains from amongst an organism complex have also been discussed.Importance Sensory proteins (SPs) act as sensors and actuators for a cell and participate in important mechanisms pertaining to bacterial survival, adaptation and virulence. Therefore, bacterial species residing in similar ecological niches or those sharing common pathotypes are expected to exhibit similar SP signatures. We have investigated profiles of SPs in different species of Escherichia coli and present in this article 'Sensory Protein Index' (SPI), a metric for quantifying the abundance or distribution of SPs across bacterial genomes which could fairly indicate the virulence potency of a bacterium. SPI could find use in characterizing hereto uncultured strains and bacterial complexes, as a biomarker for disease diagnostics, evaluating the effect of therapeutic interventions, assessing effects of ecological alterations, etc.Grouping the studied strains of E. coli on the basis of the frequency of occurrence of SPs in their genomes, indeed could fairly replicate the stratification of these strains on the basis of their phylotypes. In addition, E. coli strains belonging to same pathotypes were also seen to share similar SP signatures. Furthermore, SPI was seen to be an indicator to the pathogenic potency of E. coli strains. The SPI metric is expected to be useful in the (pathogenic) characterization of hereto uncultured strains which are obtained and routinely sequenced in host microbiome analysis projects, or from amongst an ensemble of microbial organisms constituting a biospecimen. Thus, the possibilities of using SPI as a biomarker of diagnosis of a disease or the outcome of a therapeutic intervention cannot be ruled out. Further, SPIs obtained from longitudinal ecological sample has the potential to serve as key indicators of environmental changes. Such changes in the environment are often detrimental to the resident biome and methods for timely detection of environmental changes hold huge socio-economic benefits.