Chemolithoautotrophy in the marine, magnetotactic bacterial strains MV-1 and MV-2.
Magnetite-producing magnetotactic bacteria collected from the oxic-anoxic transition zone of chemically stratified marine environments characterized by O2/H2S inverse double gradients, contained internal S-rich inclusions resembling elemental S globules, suggesting they oxidize reduced S compounds that could support autotrophy. Two strains of marine magnetotactic bacteria, MV-1 and MV-2, isolated from such sites grew in O2-gradient media with H2S or thiosulfate (S2O3(2-)) as electron sources and O2 as electron acceptor or anaerobically with S2O3(2-) and N2O as electron acceptor, with bicarbonate (HCO3-)/CO2 as sole C source. Cells grown with H2S contained S-rich inclusions. Cells oxidized S2O3(2-) to sulfate (SO4(2-)). Both strains grew microaerobically with formate. Neither grew microaerobically with tetrathionate (S4O6(2-)), methanol, or Fe2+ as FeS, or siderite (FeCO3). Growth with S2O3(2-) and radiolabeled 14C-HCO3- showed that cell C was derived from HCO3-/CO2. Cell-free extracts showed ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) activity. Southern blot analyses indicated the presence of a form II RubisCO (cbbM) but no form I (cbbL) in both strains. cbbM and cbbQ, a putative post-translational activator of RubisCO, were identified in MV-1. MV-1 and MV-2 are thus chemolithoautotrophs that use the Calvin-Benson-Bassham pathway. cbbM was also identified in Magnetospirillum magnetotacticum. Thus, magnetotactic bacteria at the oxic-anoxic transition zone of chemically stratified aquatic environments are important in C cycling and primary productivity.
Bazylinski
Dennis A
DA
Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011, USA. dbazylin@iastate.edu
Dean
Annette J
AJ
Williams
Timothy J
TJ
Long
Linda Kimble
LK
Middleton
Shawna L
SL
Dubbels
Bradley L
BL
D000595:Amino Acid Sequence; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D006090:Gram-Negative Bacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000378:metabolism; D008280:Magnetics; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012623:Seawater / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013885:Thiosulfates / Q000378:metabolism
D001426:Bacterial Proteins; D002352:Carrier Proteins; C092405:CbbQ protein, bacteria; D003470:Culture Media; D013885:Thiosulfates; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase; D010100:Oxygen; D006862:Hydrogen Sulfide