dictyNews
Electronic Edition
Volume 39, number 13
May 3, 2013

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Abstracts
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Hydrolysis of aromatic beta-glucosides by non-pathogenic bacteria
confers a chemical weapon against predators

Robert Sonowal, Krithi Nandimath, Sucheta S. Kulkarni, Sandhya P. Koushika,
Vidyanand Nanjundiah, and S. Mahadevan*

(* Corresponding author; Department of Molecular Reproduction, Development
and Genetics, Indian Institute of Science, Bangalore 560 012, India)


Proceedings of the Royal Society of London Series B., in press

Bacteria present in natural environments such as soil have evolved
multiple strategies to escape from predation. We report that natural
isolates of Enterobacteriaceae that actively hydrolyze plant-derived
aromatic beta-glucosides such as salicin, arbutin and esculin, are able
to avoid predation by the bacteriovorous amoeba Dictyostelium discoideum
and nematodes of multiple genera belonging to the family Rhabditidae. This
advantage can be observed under laboratory culture conditions as well as
in the soil environment. The aglycone moiety released by the hydrolysis of
beta-glucosides is toxic to predators and acts via the dopaminergic
receptor Dop-1 in the case of C. elegans. While soil isolates of nematodes
belonging to the family Rhabditidae are repelled by the aglycone,
laboratory strains and natural isolates of Caenorhabditis sp. are attracted 
to the compound, mediated by receptors that are independent of Dop-1, 
leading to their death. The beta-glucosides-positive (Bgl+) bacteria that are 
otherwise non-pathogenic can obtain additional nutrients from the dead 
predators, thereby switching their role from prey to predator. This study 
also offers an evolutionary explanation for the retention by bacteria of 
'cryptic' or 'silent' genetic systems such as the bgl operon.

 
Submitted by Vidyanand Nanjundiah [vidya@ces.iisc.ernet.in]
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[End dictyNews, volume 39, number 13]