The effect of organic matter and oxygen on the degradation of bacterial membrane lipids in marine sediments |
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Institution: | 1. Departamento de Ecología y Biología Animal, Facultad de Ciencias del Mar, Campus Lagoas Marcosende s/n, 36310 Vigo, Spain;2. Instituto Universitario de Investigación del Agua, Universidad de Granada, C/ Ramón y Cajal, 4, 18071 Granada, Spain;3. Departamento de Ecología, Facultad de Ciencias, Universidad de Granada, Campus Fuentenueva s/n, 18071 Granada, Spain;5. Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China |
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Abstract: | The biodegradation of purified radiolabelled membrane lipids from a methanogenic bacterium and a pseudomonad were investigated in mangrove, beach and high marsh marine sediments under aerobic and anaerobic conditions. The effect of organic matter on the amount and rate of degradation was also examined by supplementing beach sediments with humic acids. In aerobic sediments, CO2 was the major product of lipid degradation while under anaerobic conditions both CO2 and CH4 were major end products and the overall rates were reduced (up to 40%) relative to aerobic conditions. Total bacterial numbers increased during all incubations with the largest increases occurring in anaerobic sediments supplemented with humic acids. No lipid degradation occurred in aerobic or anaerobic sediments treated with formaldehyde or autoclaving. In low organic beach sediments, the ester-linked phospholipid of the pseudomonad was degraded much more rapidly than the diphytanyl glycerol diether of the methanogen with 69% of the phospholipid degraded in 96 hours versus only 4% of the methanogen lipid. Lipid degradation in both aerobic and anaerobic sediments was highly correlated to organic matter content with increasing amounts of organic matter inhibiting degradation. Long incubations (75 days) of the diphytanyl glycerol ether resulted in 51% degraded to CO2 in low (0.5%) organic mangrove sediments while only 9% was mineralized in high (10.8%) organic marsh sediments. Physicochemical sorption of membrane lipids to the organic matrix is proposed as a mechanism which protects membrane lipids from microbial attack and degradation. |
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