Shifts in microbial community structure and function in light‐ and dark‐grown biofilms driven by warming

Abstract

Biofilms are dynamic players in biogeochemical cycling in running waters and are subjected to environmental stressors like those provoked by climate change. We investigated whether a 2°C increase in flowing water would affect prokaryotic community composition and heterotrophic metabolic activities of biofilms grown under light or dark conditions. Neither light nor temperature treatments were relevant for selecting a specific bacterial community at initial phases (7-day-old biofilms), but both variables affected the composition and function of mature biofilms (28-day-old). In dark-grown biofilms, changes in the prokaryotic community composition due to warming were mainly related to rotifer grazing, but no significant changes were observed in functional fingerprints. In light-grown biofilms, warming also affected protozoan densities, but its effect on prokaryotic density and composition was less evident. In contrast, heterotrophic metabolic activities in light-grown biofilms under warming showed a decrease in the functional diversity towards a specialized use of several carbohydrates. Results suggest that prokaryotes are functionally redundant in dark biofilms but functionally plastic in light biofilms. The more complex and self-serving light-grown biofilm determines a more buffered response to temperature than dark-grown biofilms. Despite the moderate increase in temperature of only 2°C, warming conditions drive significant changes in freshwater biofilms, which responded by finely tuning a complex network of interactions among microbial populations within the biofilm matrix.

Functional diversity of algal communities from headwater grassland streams: How does it change following afforestation?

“…However, a previous study in the area found that water chemistry was similar between grassland and afforested streams and that nutrient content was low and similar in both stream types during two successive years (on six dates covering fall, winter and spring) (Farley et al 2008). Water temperature could be acting in the same way as current velocity, accelerating biofilm formation and stimulating metabolism (Díaz Villanueva et al 2011;Romaní et al 2014). In our study, although water temperature did not differ between stream types, it was higher during the high water period, which coincided with summer.…”

The ecology and biogeochemistry of stream biofilms

“…Other bacteria that are commonly found in stream biofilms, but at lower relative abundance, include Gammaproteobacteria, Deltaproteobacteria, Actinobacteria, Firmicutes, Gemmatimonadetes, Verrucomicrobia, Planctomycetes and DeinococcusThermus. Finally, next-generation sequencing data suggest that archaea constitute only a minor component of stream biofilms 26,32,33 . This finding contrasts with earlier studies using fluorescence in situ hybridization that reported archaea as notable contributors to biofilm communities in oligotrophic glacier-fed streams 34 and nutrient-rich streams 35 .…”

“…Next-generation sequencing data of 16S rRNA genes (that is, bacterial taxonomic marker genes) of samples from benthic and hyporheic biofilms are becoming increasingly available [25][26][27] , which has enabled a more detailed understanding of the composition and diversity patterns of bacterial communities within stream biofilms. These data suggest that the Proteobacteria biopolymers, such as cellulose and chitin 28,29 , that contribute to the high molecular weight fraction of DOM in streams.…”

“…Microorganisms in streams are also major components of the nitrogen cycle as they denitrify nitrate that they receive from catchment and emit the resulting nitrous oxide or nitrogen gas into the atmosphere 11,12 . Next-generation sequencing data of 16S rRNA genes (that is, bacterial taxonomic marker genes) of samples from benthic and hyporheic biofilms are becoming increasingly available [25][26][27] , which has enabled a more detailed understanding of the composition and diversity patterns of bacterial communities within stream biofilms. These data suggest that the Proteobacteria Furthermore, depending on the turbulence of the water overlying the biofilms, the biofilm canopy can differentiate into streamers (see below), which can entail microscale shifts in bacterial community composition.…”

Pseudo-Second-Order Calcium-Mediated Cryptosporidium parvum Oocyst Attachment to Environmental Biofilms

“…Thus, the higher temperatures in Indian Creek likely impacted bacterial species composition in epilithic biofilms (49). Romaní et al (26) reported that warmer temperatures significantly reduced ␤-glucosidase activity of river biofilms and that biofilms showed a significant decrease in functional diversity and metabolic specialization under conditions of light exposure and high temperatures. Villanueva et al (50) showed that thicker biofilms and increased heterotrophic utilization of polysaccharides and peptides were more common in warmer rivers.…”