Abstract
The wide use of pesticides in agriculture expose microbiota to stressful conditions that require the development of survival strategies. The bacterial response to many pollutants has not been elucidated in detail, as well as the evolutionary processes that occur to build adapted communities. The purpose of this study was to evaluate the bacterial population structure and adaptation strategies in planktonic and biofilm communities in limited environments, as tanks containing water used for washing herbicide containers. This biodiversity, with high percentage of nonculturable microorganisms, was characterized based on habitat and abiotic parameters using molecular and bioinformatics tools. According to water and wastewater standards, the physicochemical conditions of the tank water were inadequate for survival of the identified bacteria, which had to develop survival strategies in this hostile environment. The biodiversity decreased in the transition from planktonic to biofilm samples, indicating a possible association between genetic drift and selection of individuals that survive under stressful conditions, such as heating in water and the presence of chlorine, fluorine and agrochemicals over a six-month period. The abundance of Enterobacter, Acinetobacter and Pseudomonas in biofilms from water tanks was linked to essential processes, deduced from the genes attributed to these taxonomic units, and related to biofilm formation, structure and membrane transport, quorum sensing and xenobiotic degradation. These characteristics were randomly combined and fixed in the biofilm community. Thus, communities of biofilm bacteria obtained under these environmental conditions serve as interesting models for studying herbicide biodegradation kinetics and the prospects of consortia suitable for use in bioremediation in reservoirs containing herbicide-contaminated wastewater, as biofilters containing biofilm communities capable of degrading herbicides.
Highlights
The field of environmental microbiology, including the composition, structure and function of microbial communities in nature, has been gaining interest in academia over the last few years (Zhou et al, 2015)
Three types of information were analyzed to obtain insights regarding the adaptive strategies used by different bacterial communities in response to the contaminated environments used in this study: physicochemical characteristics of the environment, taxonomic composition at the time of collection, and survey of characteristics associated with survival of the identified taxonomic units
The communities were characterized as tank biofilm, flask biofilm, and planktonic communities, and all of these communities were obtained from the pre- and postheating samples and formed at different times
Summary
The field of environmental microbiology, including the composition, structure and function of microbial communities in nature, has been gaining interest in academia over the last few years (Zhou et al, 2015). Contaminated environments expose microbiota to stressful and selective conditions, and microorganisms can undergo structural and metabolic adaptations to survive under these conditions (Olson et al, 2017) These adaptive strategies are linked at the cellular level to specific microbial populations, which results in different responses to compounds such as pesticides (Prione et al, 2016; Dobrzanski et al, 2018) and allows their use in biotechnological processes to help degrade them in the environment (Martins et al, 2007; Silva et al, 2007; Olchanheski et al, 2014). Advances in genomics and metagenomics, marker genes, 16S rRNA gene sequencing and other molecular approaches are essential for predicting soil microbiome functions and improving agriculture production (Fierer, 2017) These approaches are fundamental to the creation of genomic libraries that allow the identification and isolation of enzymes with different biocatalytic activities from culturable strains and thereby allow their biotechnological exploitation (Al-Amoudi et al, 2016; Madhavan et al, 2017). Knowledge of the taxonomic structure of a microbiome increases the reliable handling of its latent biotechnological potential (Ji et al, 2017; Ofaim et al, 2017)
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