Monitoring Diel Variations of Physiological Status and Bacterial Diversity in an Estuarine Microbial Mat: An Integrated Biomarker Analysis
Microbial mats are highly productive microbial systems and a source of not-yet characterized microorganisms and metabolic strategies. In this article, we introduced a lipid biomarker/microbial isolation approach to detect short-term variations of microbial diversity, physiological and redox status, and also characterize lipid biomarkers from specific microbial groups that can be further monitored. Phospholipid fractions (PLFA) were examined for plasmalogens, indicative of certain anaerobes. The glycolipid fraction was processed for polyhydroxyalkanoates (PHA) and the neutral lipid fraction was used to evaluate respiratory quinone content. Data demonstrate an increase in the metabolic stress, unbalanced growth, proportion of anaerobic bacteria and respiratory rate after the maximal photosynthetic activity. Higher accumulation of polyhydroxyalkanoates at the same sampling point also suggested a situation of carbon storage by heterotrophs closely related to photosynthetic microorganisms. Besides, the characterization of lipid biomarkers (plasmalogens, sphingolipids) from specific microbial groups provided clues about the dynamics and diversity of less-characterized mat members. In this case, lipid analyses were complemented by the isolation and characterization of anaerobic spore formers and sulfate reducers to obtain insight into their affiliation and lipid composition. The results revealed that temporal shifts in lipid biomarkers are indicative of an intense change in the physiology, redox condition, and community composition along the diel cycle, and support the hypothesis that interactions between heterotrophs and primary producers play an important role in the carbon flow in microbial mats.
KeywordsSphingoid Base Respiratory Quinone Ebro Delta Neutral Lipid Fraction Total PLFA
This paper is dedicated to the memory of David C. White: “Thank you for being a friend and mentor, we will miss you.” We thank Mercè Piqueras and Wendy Ran for useful suggestions. We are grateful to the Center for Biomarker Analysis (TN, USA) staff for advice and technical assistance. This research was supported by Spanish MCyT grant BOS2002-02944 and MEC CGL2005-04990, and by grant DE-FC02-96ER62278, from the Office of Biological and Environmental Research (OBER) and the Natural and Accelerated Bioremediation Research (NABIR) Program. LV was recipient of a scholarship from the Spanish MECD (AP2001-0953).
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