Uncultured giant sulfur bacteria of the genus Achromatium

Head, Ian M.

doi:10.1016/s0168-6496(00)00059-3

Cited by 13 publications

(17 citation statements)

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“…A vesicle-based formation of calcite has been suggested for Achromatium sp., a giant sulfur-oxidizing bacterium belonging to Gammaproteobacteria and remarkable for its ability to accumulate micrometer-large intracellular crystals of calcite [57]. Based on TEM analyses, Head et al [58] proposed that some calcite inclusions within A. oxaliferum cells were surrounded by membranes, although preparation of thin sections of cells often resulted in the loss of intracellular calcite as seen in the present study.…”

Section: Possible Involvement Of a Membrane-limited Compartment In Thmentioning

confidence: 44%

Biomineralization Patterns of Intracellular Carbonatogenesis in Cyanobacteria: Molecular Hypotheses

Margaret-Oliver

Cam

et al. 2016

Minerals

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Abstract:The recent discovery of intracellular carbonatogenesis in several cyanobacteria species has challenged the traditional view that this process was extracellular and not controlled. However, a detailed analysis of the size distribution, chemical composition and 3-D-arrangement of carbonates in these cyanobacteria is lacking. Here, we characterized these features in Candidatus Gloeomargarita lithophora C7 and Candidatus Synechococcus calcipolaris G9 by conventional transmission electron microscopy, tomography, ultramicrotomy, and scanning transmission X-ray microscopy (STXM). Both Ca. G. lithophora C7 and Ca. S. calcipolaris G9 formed numerous polyphosphate granules adjacent or engulfing Ca-carbonate inclusions when grown in phosphate-rich solutions. Ca-carbonates were scattered within Ca. G. lithophora C7 cells under these conditions, but sometimes arranged in one or several chains. In contrast, Ca-carbonates formed at cell septa in Ca. S. calcipolaris G9 and were segregated equally between daughter cells after cell division, arranging as distorted disks at cell poles. The size distribution of carbonates evolved from a positively to a negatively skewed distribution as particles grew. Conventional ultramicrotomy did not preserve Ca-carbonates explaining partly why intracellular calcification has been overlooked in the past. All these new observations allow discussing with unprecedented insight some nucleation and growth processes occurring in intracellularly calcifying cyanobacteria with a particular emphasis on the possible involvement of intracellular compartments and cytoskeleton.

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Section: Possible Involvement Of a Membrane-limited Compartment In Thmentioning

confidence: 44%

Biomineralization Patterns of Intracellular Carbonatogenesis in Cyanobacteria: Molecular Hypotheses

Margaret-Oliver

Cam

et al. 2016

Minerals

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“…The giant sulphur bacterium Achromatium oxaliferum displays a characteristic rolling motion that presumably also serves for orientation in oxygen gradients (Head et al , 2000). The details of this behaviour, however, remain to be studied.…”

Section: Oxygen Sensing and Motile Responsesmentioning

confidence: 99%

Oxygen and the Spatial Structure of Microbial Communities

2008

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Oxygen has two faces. On one side it is the terminal electron acceptor of aerobic respiration - the most efficient engine of energy metabolism. On the other hand, oxygen is toxic because the reduction of molecular O2 creates reactive oxygen species such as the superoxide anion, peroxide, and the hydroxyl radical. Probably most prokaryotes, and virtually all eukaryotes, depend on oxygen respiration, and we show that the ambiguous relation to oxygen is both an evolutionary force and a dominating factor driving functional interactions and the spatial structure of microbial communities.We focus on microbial communities that are specialised for life in concentration gradients of oxygen, where they acquire the full panoply of specific requirements from limited ranges of PO2, which also support the spatial organisation of microbial communities. Marine and lake sediments provide examples of steep O2 gradients, which arise because consumption or production of oxygen exceeds transport rates of molecular diffusion. Deep lakes undergo thermal stratification in warm waters, resulting in seasonal anaerobiosis below the thermocline, and lakes with a permanent pycnocline often have permanent anoxic deep water. The oxycline is here biologically similar to sediments, and it harbours similar microbial biota, the main difference being the spatial scale. In sediments, transport is dominated by molecular diffusion, and in the water column, turbulent mixing dominates vertical transport. Cell size determines the minimum requirement of aerobic organisms. For bacteria (and mitochondria), the half-saturation constant for oxygen uptake ranges within 0.05-0.1% atmospheric saturation; for the amoeba Acanthamoeba castellanii it is 0.2%, and for two ciliate species measuring around 150 microm, it is 1-2 % atmospheric saturation. Protection against O2 toxicity has an energetic cost that increases with increasing ambient O2 tension. Oxygen sensing seems universal in aquatic organisms. Many aspects of oxygen sensing are incompletely understood, but the mechanisms seem to be evolutionarily conserved. A simple method of studying oxygen preference in microbes is to identify the preferred oxygen tension accumulating in O2 gradients. Microorganisms cannot sense the direction of a chemical gradient directly, so they use other devices to orient themselves. Different mechanisms in different prokaryotic and eukaryotic microbes are described. In O2 gradients, many bacteria and protozoa are vertically distributed according to oxygen tension and they show a very limited range of preferred PO2. In some pigmented protists the required PO2 is contingent on light due to photochemically generated reactive oxygen species. In protists that harbour endosymbiotic phototrophs, orientation towards light is mediated through the oxygen production of their photosynthetic symbionts. Oxygen plays a similar role for the distribution of small metazoans (meiofauna) in sediments, but there is little experimental evidence for this. Thus the oxygenated sediments surrounding ventil...

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“…These organisms thrive under microaerophilic conditions, and one strain can couple sulfide and thiosulfate oxidation to N07 reduction (Timmer-Ten Hoor, 1975). Another exceptional genus of sulfide-oxidizing Eubacteria is Achromatium, a facultative autotroph that stores S° and calcite intracellularly (Head et al, 2000) and is found in freshwater, brackish, and marine environments. The three known species that belong to this genus all have mixotrophic growth capabilities.…”

Section: Single-cell Colorless Sulfur Bacteriamentioning

confidence: 99%