Biochemical Function and Ecological Significance of Novel Bacterial Lipids in Deep-Sea Procaryotes

TLDR

Long‑chain polyunsaturated fatty acids, previously thought absent in prokaryotes except a single marine Flexibacter species, are now detected in deep‑sea bacteria and are key nutrients in abyssal food webs. The authors analyzed membrane lipid composition in 11 deep‑sea isolates, finding that PUFA content rises with growth pressure in barophilic strains and with decreasing temperature in a psychrophilic Vibrio strain. The isolates exhibit unusually high long‑chain PUFA levels, indicating that these lipids help preserve optimal membrane fluidity across varying temperatures and pressures.

Abstract

The fatty acid composition of the membrane lipids in 11 deep-sea bacterial isolates was determined. The fatty acids observed were typical of marine vibrios except for the presence of large amounts of long-chain polyunsaturated fatty acids (PUFAs). These long-chain PUFAs were previously thought to be absent in procaryotes, with the notable exception of a single marine Flexibacter sp. In three barophilic strains tested at 2°C, there was a general increase in the relative amount of PUFAs as pressure was increased from a low growth pressure towards the optimal growth pressure. In Vibrio marinus MP-1, a psychrophilic strain, PUFAs were found to increase as a function of decreasing temperature at constant atmospheric pressure. These results suggest the involvement of PUFAs in the maintenance of optimal membrane fluidity and function over environmentally relevant temperatures and pressures. Furthermore, since these lipids are essential nutrients for higher taxa and are found in large amounts in the lipids of deep-sea vertebrates and invertebrates, an important, specific role for deep-sea bacteria in abyssal food webs is implicated.