Diversity and Distribution of Volatile Secondary Metabolites Throughout Bacillus subtilis Isolates.

Marco Kai

doi:10.3389/fmicb.2020.00559

Abstract

Bacillus subtilis releases a broad range of volatile secondary metabolites, which are considered as long- and short distance infochemical signals mediating inter- and intra-specific processes. In addition, they often show antimicrobial or antifungal activities. This review attempts to summarize yet known volatile secondary metabolites produced and emitted by Bacillus subtilis isolates focusing on the structural diversity and distribution patterns. Using in vitro volatile-collection systems, 26 strains of B. subtilis isolated from different habitats were found to produce in total 231 volatile secondary metabolites. These volatile secondary metabolites comprised mainly hydrocarbons, ketones, alcohols, aldehydes, ester, acids, aromatics, sulfur- and nitrogen-containing compounds. Reviewed data revealed to a great extent isolate-specific emission patterns. The production and release of several volatile bioactive compounds was retained in isolates of the species B. subtilis, while volatiles without a described function seemed to be isolate-specifically produced. Detailed analysis, however, also indicated that the original data were strongly influenced by insufficient descriptions of the bacterial isolates, heterogeneous and poorly documented culture conditions as well as sampling techniques and inadequate compound identification. In order to get deeper insight into the nature, diversity, and ecological function of volatile secondary metabolites produced by B. subtilis, it will be necessary to follow well-documented workflows and fulfill state-of-the-art standards to unambiguously identify the volatile metabolites. Future research should consider the dynamic of a bacterial culture leading to differences in cell morphology and cell development. Single cell investigations could help to attribute certain volatile metabolites to defined cell forms and developmental stages.

Highlights

Bacillus subtilis is a rod-shaped, aerobic, endospore forming Gram-positive bacterium that colonizes the soil and often occurs plant-associated
Several hundred wild-type strains of B. subtilis have been analyzed for non-volatile metabolites (Stein, 2005), the present review will give a first overview of volatile secondary metabolites
The evaluation and interpretation of potential production and emission of bacterial metabolites in nature should always be done in close consideration of culture conditions, since they determine bacterial growth and development, which could influence the production of volatile secondary metabolites as it was already shown for other bacterial species (Kai et al, 2009; Blom et al, 2011; Weise et al, 2012; Ratiu et al, 2017b)

Summary

INTRODUCTION

Bacillus subtilis is a rod-shaped, aerobic, endospore forming Gram-positive bacterium that colonizes the soil and often occurs plant-associated. Volatile Metabolites From Bacillus subtilis essential need for them in growth, development, or reproduction of the organisms Their absence can cause damage or alter the organism or population, since secondary metabolites function as communication signals, antibiotics or siderophores (Vining, 1990; Davies, 2006; Yim et al, 2007; Ratcliff and Denison, 2011; Sansinenea and Ortiz, 2011). Bacteria in general release a high diversity of volatile secondary metabolites including hydrocarbons, ketones, alcohols, sulfur- and nitrogen containing compounds, terpenes, and others (Schulz and Dickschat, 2007; Lemfack et al, 2014, 2018) These metabolites are primarily considered as longand short distance infochemicals mediating inter- and intraspecific interactions, but they act as antimicrobial or antifungal agents (Kai et al, 2009; Schmidt et al, 2017; SchulzBohm et al, 2017). Several hundred wild-type strains of B. subtilis have been analyzed for non-volatile metabolites (Stein, 2005), the present review will give a first overview of volatile secondary metabolites

Methods

Findings

CONCLUSION