UV radiation and organic matter composition shape bacterial functional diversity in sediments

Ellard R Hunting,Der Geest,Daan Mes,Maarten Van Gemert,Wim Admiraal,Christopher M White,Michiel H S Kraak,Harm G Van,Eva Stam

doi:10.3389/fmicb.2013.00317

Abstract

UV radiation and organic matter (OM) composition are known to influence the species composition of bacterioplankton communities. Potential effects of UV radiation on bacterial communities residing in sediments remain completely unexplored to date. However, it has been demonstrated that UV radiation can reach the bottom of shallow waters and wetlands and alter the OM composition of the sediment, suggesting that UV radiation may be more important for sediment bacteria than previously anticipated. It is hypothesized here that exposure of shallow OM-containing sediments to UV radiation induces OM source-dependant shifts in the functional composition of sediment bacterial communities. This study therefore investigated the combined influence of both UV radiation and OM composition on bacterial functional diversity in laboratory sediments. Two different OM sources, labile and recalcitrant OM, were used and metabolic diversity was measured with Biolog GN. Radiation exerted strong negative effects on the metabolic diversity in the treatments containing recalcitrant OM, more than in treatments containing labile OM. The functional composition of the bacterial community also differed significantly between the treatments. Our findings demonstrate that a combined effect of UV radiation and OM composition shapes the functional composition of microbial communities developing in sediments, hinting that UV radiation may act as an important sorting mechanism for bacterial communities and driver for bacterial functioning in shallow waters and wetlands.

Highlights

Several studies have demonstrated that UV radiation may affect bacterioplankton communities (e.g., Baldy et al, 2002; Piccini et al, 2009; Zepp et al, 2011), exerting detrimental effects on DNA or extracellular enzymes (e.g., Santos et al, 2012a; for review, see Ruiz-González et al, 2013)
In addition to the number of substrates used by the bacterial community, we assessed which set of substrates was used by the bacteria to compare the functional composition of the communities that developed during the incubation
A two-way analysis of similarities (ANOSIM) revealed that the bacterial resource niches differed significantly between treatments depending on both radiation and organic matter (OM) type, showing that the developed bacterial communities were functionally distinct

Summary

Introduction

Several studies have demonstrated that UV radiation may affect bacterioplankton communities (e.g., Baldy et al, 2002; Piccini et al, 2009; Zepp et al, 2011), exerting detrimental effects on DNA or extracellular enzymes (e.g., Santos et al, 2012a; for review, see Ruiz-González et al, 2013). UV radiation may change the chemical composition and palatability of organic matter (OM) by photodegradation (e.g., Engelhaupt et al, 2002; Sulzberger and Durisch-Kaiser, 2009) Such changes in the chemical composition of OM may subsequently cascade toward shifts in bacterial community composition due to the interplay between bacterial resource niches (i.e., the type of substrates that are utilized) and available resources (e.g., Salles et al, 2009). This suggests that the functional composition of bacterial communities may change when exposed to UV radiation. Since composition of the available OM is one of the main drivers of bacterial community composition (e.g., Hättenschwiler and Vitousek, 2000; Myers et al, 2001; Baldy et al, 2002; Docherty et al, 2006; Kampfraath et al, 2012), and UV radiation differentially affects different OM sources (Benner and Kaiser, 2011), we assessed the effects of UV exposure on bacterial communities on two OM sources that differ in chemical composition

Methods

Results

Discussion

Conclusion