The effect of light intensity and shear stress on microbial biostabilization and the community composition of natural biofilms

Abstract

Abstract:Biofilms constitute an important issue in microbial ecology, due to their high ecological and economic relevance, but the impact of abiotic conditions and microbial key players on the development and functionality of a natural biofilm is still little understood. This study investigated the effects of light intensity (LI) and bed shear stress (BSS) and the role of dominant microbes during the formation of natural biofilms and particularly the process microbial biostabilization. A comprehensive analysis of microbial biomass, extracellular polymeric substances produced, and the identification of dominant bacterial and algal species was correlated with assessment of biofilm adhesiveness/stability. LI and BSS impacted the biofilms in very different ways: biofilm adhesiveness significantly increased with LI and decreased with BSS. Moreover, microbial biomass and the functional organization of the bacterial community increased with LI, while the dynamics in the bacterial community increased with BSS. Most stable biofilms were dominated by sessile diatoms like Achnanthidium minutissimum or Fragilaria pararumpens and bacteria with either filamentous morphology, such as Pseudanabaena biceps, or a potential high capacity for extracellular polymeric-substance production, such as Rubrivivax gelatinosus. In contrast, microbes with high motility, such as Nitzschia fonticola, Pseudomonas fluorescens, and Caulobacter vibrioides, dominated the least adhesive biofilms. Their movement and potential antibiotic production could have had a disruptive impact on the biofilm matrix, which decreased its stability. This is the first study to unveil the link between abiotic conditions and resulting shifts in key microbial players to impact the ecosystem-service microbial biostabilization.

Strong influence of climatic extremes on diversity of benthic algae and cyanobacteria in a lowland intermittent stream

“…This diversity loss was due to the dominance of small diatom taxa, such as the typically pioneer, unicellular, strongly attached Achnanthidium minutissimum and the unicellular but weakly attached and mobile Navicula species. The tolerance of A. minutissimum against disturbances is a well‐known phenomenon: its small size makes this species a fast and efficient coloniser even under low supply and it is adapted well to the shear forces caused by water flow as well as the extremes in light intensity (B‐Béres et al, 2014; Schmidt et al, 2018; Stenger‐Kovács et al, 2006). Most of the Navicula species that dominated the benthos in the HDC period were small‐sized organisms.…”

The effect of cyclic variation of shear stress on non‐cohesive sediment stabilization by microbial biofilms: the role of ‘biofilm precursors’

“…Bacterial biofilms were generally a thin surface layer which was sheared away within a very short space of time (e.g. A possible explanation is related to light intensity Schmidt et al, 2018). This was also shown in the erosion curves ( Figure 4) where a long period of erosion with low erosion rates was observed in algal systems before any evident increase of SSC.…”

“…As a result, after 22 days the SSC of the bio-sedimentary bed increased from zero to the final value of 45 kg m -3 within a very short time period (last step of applied BSS). A possible explanation is related to light intensity Schmidt et al, 2018). Since the vertical penetration of light decreases rapidly with bed depth, microalgae communities are often confined to the sediment surface, in contrast to bacterial communities (Chen et al, 2017a(Chen et al, , 2017b) that may be more distributed into the sediment and not dependent on light energy.…”

“…As influenced by microbial metabolism, the bio-sedimentary matrix responds to both ecological (light, nutrients, pollutants) and physical drivers (hydrodynamic conditions and meteorological forcing) and exhibits more complex and variable characteristics than abiotic systems (Montague, 1986;Celmer et al, 2008;Paterson et al, 2008;Stone et al, 2008;Fang et al, 2017;Chen et al, 2017b;Schmidt et al, 2018). For instance, field observations on a tidal flat show that natural biofilms are heterogeneously distributed and that biofilm thickness varies across the flat, leading to a highly complex surface structure ( Figure 1).…”

Biomass index and viscosity values of Moringa oleifera that influenced by Enterococcus faecalis

“…15 In addition, the decrease in biomass from bacterial activity with antibacterials indicates that antibacterial agents have an excellent ability to disrupt metabolism and reduce the biostability of the bacterial environment. 16 Table 1 reports that a concentration of 12.5% has a high viscosity, meaning that Moringa leaves can provide a better response to the development of E. faecalis because there is no biosynthesis or decomposition of antibacterial substances. Low viscosity can indicate bacterial metabolism, meaning that bacterial activity is more dominant than the antibacterial role.…”