Norspermidine Is Not a Self-Produced Trigger for Biofilm Disassembly

Laura Hobley,Sok Ho Kim,Yukari Maezato,Susan Wyllie,Alan H Fairlamb,Nicola R Stanley-Wall,Anthony J Michael

doi:10.1016/j.cell.2014.01.012

Laura Hobley, Sok Ho Kim + Show 5 more

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https://doi.org/10.1016/j.cell.2014.01.012

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Abstract

SummaryFormation of Bacillus subtilis biofilms, consisting of cells encapsulated within an extracellular matrix of exopolysaccharide and protein, requires the polyamine spermidine. A recent study reported that (1) related polyamine norspermidine is synthesized by B. subtilis using the equivalent of the Vibrio cholerae biosynthetic pathway, (2) exogenous norspermidine at 25 μM prevents B. subtilis biofilm formation, (3) endogenous norspermidine is present in biofilms at 50–80 μM, and (4) norspermidine prevents biofilm formation by condensing biofilm exopolysaccharide. In contrast, we find that, at concentrations up to 200 μM, exogenous norspermidine promotes biofilm formation. We find that norspermidine is absent in wild-type B. subtilis biofilms at all stages, and higher concentrations of exogenous norspermidine eventually inhibit planktonic growth and biofilm formation in an exopolysaccharide-independent manner. Moreover, orthologs of the V. cholerae norspermidine biosynthetic pathway are absent from B. subtilis, confirming that norspermidine is not physiologically relevant to biofilm function in this species.

Highlights

The ability of microbial cells to colonize a habitat is frequently dependent on biofilm formation, a process by which microbial cells form a sessile community encased in a self-produced extracellular matrix (Costerton et al, 1995; Davey and O’Toole, 2000; Flemming and Wingender, 2010)
Formation of Bacillus subtilis biofilms, consisting of cells encapsulated within an extracellular matrix of exopolysaccharide and protein, requires the polyamine spermidine
A recent study reported that (1) related polyamine norspermidine is synthesized by B. subtilis using the equivalent of the Vibrio cholerae biosynthetic pathway, (2) exogenous norspermidine at 25 mM prevents B. subtilis biofilm formation, (3) endogenous norspermidine is present in biofilms at 50–80 mM, and (4) norspermidine prevents biofilm formation by condensing biofilm exopolysaccharide

Summary

Introduction

The ability of microbial cells to colonize a habitat is frequently dependent on biofilm formation, a process by which microbial cells form a sessile community encased in a self-produced extracellular matrix (Costerton et al, 1995; Davey and O’Toole, 2000; Flemming and Wingender, 2010). This extracellular matrix is typically composed of extracellular DNA, proteins, and exopolysaccharides that together function to adhere cells to a surface and provide protection from external physical and chemical stresses (Branda et al, 2005; Flemming and Wingender, 2010). Biofilms formed by B. subtilis manifest as robust surface-associated colonies and floating pellicles that both display a complex rugose architecture (Branda et al, 2001; Vlamakis et al, 2013)

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