Population structure determined by comparative amplicon gene sequencing in biofilm and planktonic bacterial communities from pesticide-contaminated water

Molecular and bioinformatics tools for research are very important for biodiversity characterization in contaminated environments due the presence of a high percentage of nonculturable microorganisms. The wide use of pesticides in agriculture exposes microbiomes to stressful and selective conditions that demand survival strategies such as biofilm formation. The purpose of this work was to evaluate the bacterial population structure in planktonic and biofilm communities of water that was used for washing the packaging of herbicides and stored for six months in tanks. This substance is highly contaminated waste. Samples of water and biofilms from tanks and biofilms developed for short times in flasks were used for DNA isolation and 16S rRNA gene sequencing. The physicochemical conditions imposed by water used for washing the containers were inadequate for killing the bacterial genera identified according to water and wastewater standards. The variation in population structure and diversity was lower in the planktonic samples than in the biofilm samples, indicating a possible combination of genetic drift and subsequent selection of individuals surviving under stressful water conditions, such as heating and contact with agrochemicals, over a six-month period. The biofilm formation in water tanks contaminated with pesticides enabled the survival of bacterial genera harboring the essential processes for adaptation to these environments; the presence of these processes was determined according to descriptions obtained from the genomic databases. This study suggests the potential of bacterial genera identified in biofilms obtained from tanks to adapt to contaminated environments through their metabolic complexity. Thus, herbicide biodegradation kinetics can be accessed through a culturable collection obtained from these communities.