Phylogenetic analysis and phenotypic characterization were used to assign a multicellular magnetotactic prokaryote the name ‘Candidatus Magnetoglobus multicellularis’. ‘Candidatus Magnetoglobus multicellularis' lives in a large hypersaline coastal lagoon from Brazil and has properties that are unique among prokaryotes. It consists of a compact assembly or aggregate of flagellated bacterial cells, highly organized in a sphere, that swim in either helical or straight trajectories. The life cycle of ‘Candidatus Magnetoglobus multicellularis' is completely multicellular, in which one aggregate grows by enlarging the size of its cells and approximately doubling the volume of the whole organism. Cells then divide synchronously, maintaining the spherical arrangement; finally the cells separate into two identical aggregates. Phylogenetic 16S rRNA gene sequence analysis showed that ‘Candidatus Magnetoglobus multicellularis' is related to the dissimilatory sulfate-reducing bacteria within the Deltaproteobacteria and to other previously described, but not yet well characterized, multicellular magnetotactic prokaryotes.
ABSTRACT
The pigment composition of “
Candidatus
Chlorothrix halophila,” a filamentous anoxygenic phototrophic bacterium found in Baja California Sur, Mexico, was determined. Previous work showed that bacteriochlorophyll
c
(BChl
c
) was the major pigment in “
Ca
. Chlorothrix halophila,” but it was not clear if this bacterium also contains BChl
a
(J. A. Klappenbach and B. K. Pierson, Arch. Microbiol.
181:
17-25, 2004). Here we show that in addition to BChl
c
, a small amount of a pigment that is spectrally indistinguishable from BChl
a
is present in cell extracts of “
Ca
. Chlorothrix halophila.” Nevertheless, the BChl
a
-like pigment from “
Ca
. Chlorothrix halophila” has a different molecular weight and a different high-performance liquid chromatography elution time than BChl
a
from other photosynthetic bacteria. Based on mass spectrometry and other spectroscopic analysis, we determined that the BChl
a
-like pigment in “
Ca
. Chlorothrix halophila” contains a tetrahydrogeranylgeraniol tail rather than the phytol tail that is present in BChl
a
. The carotenoids and major BChl
c
homologs in “
Ca
. Chlorothrix halophila” were also identified. BChls
c
were found to be farnesol esterified and geranylgeraniol esterified.