Multiple genome sequences reveal adaptations of a phototrophic bacterium to sediment microenvironments.
The bacterial genus Rhodopseudomonas is comprised of photosynthetic bacteria found widely distributed in aquatic sediments. Members of the genus catalyze hydrogen gas production, carbon dioxide sequestration, and biomass turnover. The genome sequence of Rhodopseudomonas palustris CGA009 revealed a surprising richness of metabolic versatility that would seem to explain its ability to live in a heterogeneous environment like sediment. However, there is considerable genotypic diversity among Rhodopseudomonas isolates. Here we report the complete genome sequences of four additional members of the genus isolated from a restricted geographical area. The sequences confirm that the isolates belong to a coherent taxonomic unit, but they also have significant differences. Whole genome alignments show that the circular chromosomes of the isolates consist of a collinear backbone with a moderate number of genomic rearrangements that impact local gene order and orientation. There are 3,319 genes, 70% of the genes in each genome, shared by four or more strains. Between 10% and 18% of the genes in each genome are strain specific. Some of these genes suggest specialized physiological traits, which we verified experimentally, that include expanded light harvesting, oxygen respiration, and nitrogen fixation capabilities, as well as anaerobic fermentation. Strain-specific adaptations include traits that may be useful in bioenergy applications. This work suggests that against a backdrop of metabolic versatility that is a defining characteristic of Rhodopseudomonas, different ecotypes have evolved to take advantage of physical and chemical conditions in sediment microenvironments that are too small for human observation.
Oda
Yasuhiro
Y
Department of Microbiology, University of Washington, Seattle, WA 98195, USA.
Larimer
Frank W
FW
Chain
Patrick S G
PS
Malfatti
Stephanie
S
Shin
Maria V
MV
Vergez
Lisa M
LM
Hauser
Loren
L
Land
Miriam L
ML
Braatsch
Stephan
S
Beatty
J Thomas
JT
Pelletier
Dale A
DA
Schaefer
Amy L
AL
Harwood
Caroline S
CS
D000222:Adaptation, Physiological; D005618:Fresh Water; D015321:Gene Rearrangement; D016680:Genome, Bacterial; D019015:Geologic Sediments / Q000382:microbiology*; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation; D010788:Photosynthesis; D010802:Phylogeny; D012241:Rhodopseudomonas / Q000145:classification / Q000235:genetics* / Q000502:physiology; D014871:Water Microbiology