Diversity and Functions of Epilithic Riverine Biofilms

Abstract

This article relates epilithic dry- and wet-seasonal bacterial biofilm composition to water quality along Río de la Sabana near Acapulco, Mexico. Samples were taken from various locations including nearly pristine upland locations, adjacent to residential floodplain developments, and immediately upstream from an estuarine lagoon. Bacterial composition was identified through sequential DNA analysis at the phylum, class, order, and family levels, with most of these categorized as heterotrophs, autotrophs, denitrifiers, nitrogen fixers, pathogens, and/or potential bioremediators based on generalized literature-sourced assignments. The results were interpreted in terms of location by extent of effluent pollution, and by dry versus wet seasonal changes pertaining to biofilm composition, related bacterial functions, and the following water quality parameters: temperature, pH, dissolved oxygen, biological and chemical oxygen demand, fecal and total bacteria counts, methylene blue active substances, electrical conductivity, and nitrite, nitrate, ammonium, sulfate, and phosphate concentrations. It was found that epilithic bacterial biofilm diversity was richest during the wet season, was more varied in abundance along the upland locations, and was dominated by Proteobacteria and Bacteroidetes with bioremediation and pathogen functions along effluent-receiving river locations. Low-abundance families associated with anaerobic and denitrifying functions were more prevalent during the wet season, while low-abundance families associated with aerobic, N2-fixing and pH-elevating functions were more prevalent during the dry season.

Do Microorganisms in Bathing Water in Guadeloupe (French West Indies) Have Resistance Genes?

“…These results contrast with those of two previous studies, in which significant differences were observed between sampling sites [81,85] but not between sampling dates [81], which suggests that the composition of the microbial community is relatively stable over time but may vary according to the characteristics of each sampling site [81,84]. Other studies have also shown that the composition of phyla within biofilms can be influenced by pollution, seasonal variations and the physico-chemical properties of the water [54,64,76,86]. These observations highlight the sensitivity of biofilm communities not only to geographical location, and thus the environment, but also to time, particularly seasons [82,84,87].…”

“…An analysis of the biofilm microbiome characteristics from three freshwater sites showed that the predominant bacterial phyla at our study sites were Proteobacteria, Bacteriodetes, Planctomycetes, and Cyanobacteria, as reported in previous studies but with different abundances [50][51][52][53][54][55]. The predominance of Proteobacteria was highlighted in previous studies investigating surface waters [56][57][58][59][60][61] and biofilms from various environments [51,62,63] through 16S rRNA gene analysis.…”

“…Ecological interactions, nutrient availability, and local environmental conditions (T • C, pH, etc.) are factors likely to influence this dynamic [54,64,76]. Other studies have indicated that water flow [77] and oxygenation [78] contribute to the shaping of microbial communities in biofilms.…”

Wastewater microorganisms impact microbial diversity and important ecological functions of stream periphyton

“…However, we are not aware of any study that investigated the specific effect of wastewater microorganisms on this phylum. Deinococcaceae have already been associated to periphyton growing in reference (unpolluted) sites in a previous study comparing community composition along an urban pollution gradient in a stream (Pineda-Mora et al, 2020), indicating their potential sensitivity to wastewater constituents. The presence of Methylobacteriaceae and Microbacteriaceae in the Group Negative may be explained by their association with microalgae (Levy et al, 2009;Paddock et al, 2020), which seemed to be negatively impacted by wastewater microorganisms in terms of abundance (i.e.…”