Abstract
This study tests the hypothesis that surface composition influences microbial community structure and growth of biofilms. We used laboratory biofilm reactors (inoculated with a diverse subsurface community) to explore the phylogenetic and taxonomic variability in microbial communities as a function of surface type (carbonate, silicate, aluminosilicate), media pH, and carbon and phosphate availability. Using high-throughput pyrosequencing, we found that surface type significantly controlled ~70–90% of the variance in phylogenetic diversity regardless of environmental pressures. Consistent patterns also emerged in the taxonomy of specific guilds (sulfur-oxidizers/reducers, Gram-positives, acidophiles) due to variations in media chemistry. Media phosphate availability was a key property associated with variation in phylogeny and taxonomy of whole reactors and was negatively correlated with biofilm accumulation and α-diversity (species richness and evenness). However, mineral-bound phosphate limitations were correlated with less biofilm. Carbon added to the media was correlated with a significant increase in biofilm accumulation and overall α-diversity. Additionally, planktonic communities were phylogenetically distant from those in biofilms. All treatments harbored structurally (taxonomically and phylogenetically) distinct microbial communities. Selective advantages within each treatment encouraged growth and revealed the presence of hundreds of additional operational taxonomix units (OTU), representing distinct consortiums of microorganisms. Ultimately, these results provide evidence that mineral/rock composition significantly influences microbial community structure, diversity, membership, phylogenetic variability, and biofilm growth in subsurface communities.
Highlights
It is estimated that up to 99.9% of microbial biomass in a subsurface environment is attached to surfaces as biofilms (Madigan et al, 2009)
The purpose of this study is to Minerals as Habitats for Subsurface Biofilm Microorganisms characterize the mineralogical contribution to microbial diversity, investigating the contribution of different natural surface types under a range of environmental conditions
The subsurface environment is a complex blend of rocks and minerals that are generally not considered to play an active role in microbial colonization
Summary
It is estimated that up to 99.9% of microbial biomass in a subsurface environment is attached to surfaces as biofilms (Madigan et al, 2009). Growth, and specific survival strategies include and have greater implications for adjacent studies of physical properties (hydrodynamics) of bulk fluid (Kugaprasatham et al, 1992), physicochemical nature of surfaces (Dalton et al, 1994; Rogers et al, 1998; Rogers and Bennett, 2004; Carson et al, 2009; Sylvan et al, 2012), microbial community composition (Lawrence et al, 1991), and nutrient cycling and availability (primarily carbon, phosphorous, and nitrogen; Ohashi et al, 1995; Huang et al, 1998; Rogers et al, 2001). In oligotrophic environments, such as those in the subsurface, microorganisms are likely highly reliant on minerals (“mineraltrophic”) to support various biogeochemical processes (Stevens, 1997; Anderson, 2001; Chapelle et al, 2002; Edwards et al, 2005, 2012)
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