Exploring the Influence of Signal Molecules on Marine Biofilms Development.

Ruojun Wang,Pei-Yuan Qian,Haoya Tong,Yi Lan,Wei Ding,Yue Him Wong,Lexin Long,Yongxin Li,Subhasish Saha,Jin Sun,Weipeng Zhang

doi:10.3389/fmicb.2020.571400

Abstract

Microbes respond to environmental stimuli through complicated signal transduction systems. In microbial biofilms, because of complex multiple species interactions, signals transduction systems are of an even higher complexity. Here, we performed a signal-molecule-treatment experiment to study the role of different signal molecules, including N-hexanoyl-L-homoserine lactone (C6-HSL), N-dodecanoyl-L-homoserine lactone (C12-HSL), Pseudomonas quinolone signal (PQS), and cyclic di-GMP (c-di-GMP), in the development of marine biofilms. Comparative metagenomics suggested a distinctive influence of these molecules on the microbial structure and function of multi-species biofilm communities in its developing stage. The PQS-treated biofilms shared the least similarity with the control and initial biofilms. The role of PQS in biofilm development was further explored experimentally with the strain Erythrobacter sp. HKB8 isolated from marine biofilms. Comparative transcriptomic analysis showed that 314 genes, such as those related to signal transduction and biofilm formation, were differentially expressed in the untreated and PQS-treated Erythrobacter sp. HKB8 biofilms. Our study demonstrated the different roles of signal molecules in marine biofilm development. In particular, the PQS-based signal transduction system, which is frequently detected in marine biofilms, may play an important role in regulating microbe-microbe interactions and the assemblage of biofilm communities.

Highlights

Prokaryotic microbes respond to various environmental stimuli by employing signal transduction systems (Gotoh et al, 2010)
The Petri dishes with the 9-day-old biofilms were randomly divided into 11 groups: two groups were treated with C6-HSL, two groups were treated with C12-HSL, two groups were treated with c-di-GMP, two groups were treated with Pseudomonas quinolone signal (PQS), two groups were placed in seawater without any molecule treatment and defined as the “control” biofilms, and one group was immediately subjected to DNA extraction without any sort of treatment and defined as the “initial” biofilm
To test our hypothesis that signal molecules had influence on biofilm communities, N-hexanoyl-L-homoserine lactone (C6-HSL), N-dodecanoyl-L-homoserine lactone (C12-HSL), c-di-GMP, and PQS were added to biofilms pre-established in situ on plastic Petri dishes

Summary

Introduction

Prokaryotic microbes respond to various environmental stimuli by employing signal transduction systems (Gotoh et al, 2010). Pseudomonas strains are common strains in marine biofilms, and they produce the Pseudomonas quinolone signal (PQS), which could act as a signal molecule that affects bacterial interspecies behavior and communication in both Gram-positive and Gram-negative bacteria, including Escherichia coli NCIMB11943, Vibrio fischeri ES114, Proteus vulgaris NCIMB12426, and Bacillus subtilis NCTC10073 (Mooij et al, 2011). Cyclic di-GMP (c-di-GMP) is produced as a ubiquitous second messenger to control cell adhesion and persistence of multicellular communities (Jenal and Malone, 2006; Valentini and Filloux, 2016). Despite these earlier studies, the effect of signal transduction on natural marine biofilms remains unresolved

Methods

Results

Conclusion