Mechanism of lipid-body formation in prokaryotes: how bacteria fatten up.
Neutral lipid accumulation is frequently observed in some Gram-negative prokaryotes like Acinetobacter sp. and most actinomycetes, including the pathogenic Mycobacterium tuberculosis and antibiotic producing streptomycetes. We examined the formation of wax ester- and triacylglycerol (TAG)-bodies in Acinetobacter calcoaceticus and Rhodococcus opacus using microscopic, immunological and biophysical methods. A general model for prokaryotic lipid-body formation is proposed, clearly differing from the current models for the formation of lipid inclusions in eukaryotes and of poly(hydroxyalkanoic acid) (PHA) inclusions in prokaryotes. Formation of lipid-bodies starts with the docking of wax ester synthase/acyl-CoA:diacylglycerol acyltransferase (WS/DGAT) to the cytoplasm membrane. Both, analyses of in vivo and in vitro lipid-body synthesis, demonstrated the formation of small lipid droplets (SLDs), which remain bound to the membrane-associated enzyme. SLDs conglomerated subsequently to membrane-bound lipid-prebodies which are then released into the cytoplasm. The formation of matured lipid-bodies in the cytoplasm occurred by means of coalescence of SLDs inside the lipid prebodies, which are surrounded by a half-unit membrane of phospholipids.
Wältermann
Marc
M
Institut für Molekulare Mikrobiologie und Biotechnologie, Universitätsklinikum Münster, Westfälische Wilhelms-Universität, D-48149 Münster, Germany.
Hinz
Andreas
A
Robenek
Horst
H
Troyer
David
D
Reichelt
Rudolf
R
Malkus
Ursula
U
Galla
Hans-Joachim
HJ
Kalscheuer
Rainer
R
Stöveken
Tim
T
von Landenberg
Philipp
P
Steinbüchel
Alexander
A
D016954:Acinetobacter calcoaceticus / Q000254:growth & development / Q000378:metabolism*; D000217:Acyltransferases / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D003593:Cytoplasm / Q000378:metabolism; D004952:Esters / Q000378:metabolism; D002479:Inclusion Bodies / Q000378:metabolism*; D050356:Lipid Metabolism; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D012240:Rhodococcus / Q000254:growth & development / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism; D014885:Waxes / Q000378:metabolism
D004952:Esters; D014280:Triglycerides; D014885:Waxes; D000217:Acyltransferases; C079165:long-chain-alcohol O-fatty-acyltransferase