The transition from freshwater to marine iron‐oxidizing bacterial lineages along a salinity gradient on the Sheepscot River, Maine, USA. Issue 3 (12th March 2013)

• Record Type: Journal Article
• Authors: McBeth, Joyce M.; Fleming, Emily J.; Emerson, David
• Is Part Of: Environmental microbiology reports. Volume 5:Issue 3(2013:Jun.)
• Page Start: 453
• Page End: 463
• Publication Date: 2013-03-12
• Subjects: Microbial ecology -- Periodicals; Environmental Microbiology -- Periodicals; Electronic journals; 579.17
• DOI: 10.1111/1758-2229.12033
• Languages: English
• ISSNs: 1758-2229

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>Oxygen‐dependent, neutrophilic iron‐oxidizing bacteria (FeOB) are important drivers of iron transformations in marine and freshwater environments. Despite remarkable similarities in physiology and morphotype, known freshwater and marine FeOB are clustered in different classes of <italic>Proteobacteria</italic>; freshwater FeOB in the <italic>Betaproteobacteria</italic> and marine FeOB in the <italic>Zetaproteobacteria</italic>. To determine effects of salinity on these microbes, we examined the mineral biosignatures and molecular ecology of bacteria in FeOB mats collected along an estuarine salinity gradient. Light microscopy and scanning electron microscopy analyses showed the presence of iron oxide stalk and sheath structures in both freshwater and saline iron mats. Results of tagged pyrosequencing, quantitative PCR and fluorescent <italic>in situ</italic> hybridization, all based on the small subunit rRNA gene, confirmed <italic>Zetaproteobacteria</italic> were not present in freshwater mats, but were in saline mats at salinities down to 5‰. Among the <italic>Betaproteobacteria</italic>, <italic>Leptothrix</italic> spp. were only found in the freshwater mat. <italic>Gallionella</italic> spp<italic>.</italic> were limited to freshwater and low salinity mats (< 5‰). <italic>Sideroxydans</italic> sp. were salt tolerant; however, their relative abundance decreased with increasing salinity. These results suggest salinity is important in shaping the population biology of iron mat communities, and some coexistence between marine and freshwater populations occurs in brackish waters.</p> </abstract>