There are two main types of bacterial photosynthesis: oxygenic (cyanobacteria) and anoxygenic (sulfur and non-sulfur phototrophs). Molecular mechanisms of photosynthesis in the phototrophic microorganisms can differ and depend on their location and pigments in the cells. This paper describes bacteria capable of molecular oxidizing hydrogen sulfide, specifically the families Chromatiaceae and Chlorobiaceae, also known as purple and green sulfur bacteria in the process of anoxygenic photosynthesis. Further, it analyzes certain important physiological processes, especially those which are characteristic for these bacterial families. Primarily, the molecular metabolism of sulfur, which oxidizes hydrogen sulfide to elementary molecular sulfur, as well as photosynthetic processes taking place inside of cells are presented. Particular attention is paid to the description of the molecular structure of the photosynthetic apparatus in these two families of phototrophs. Moreover, some of their molecular biotechnological perspectives are discussed.
- Klíčová slova
- anaerobes, anoxygenic bacteria, detoxification, hydrogen sulfide, molecular mechanisms of photosynthesis, water environment,
- MeSH
- anaerobióza MeSH
- Chlorobi klasifikace genetika fyziologie MeSH
- Chromatiaceae klasifikace genetika fyziologie MeSH
- fototrofní procesy genetika MeSH
- fylogeneze MeSH
- síra metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
- Názvy látek
- síra MeSH
Antenna protein aggregation is one of the principal mechanisms considered effective in protecting phototrophs against high light damage. Commonly, it is induced, in vitro, by decreasing detergent concentration and pH of a solution of purified antennas; the resulting reduction in fluorescence emission is considered to be representative of non-photochemical quenching in vivo. However, little is known about the actual size and organization of antenna particles formed by this means, and hence the physiological relevance of this experimental approach is questionable. Here, a quasi-single molecule method, fluorescence correlation spectroscopy (FCS), was applied during in vitro quenching of LHCII trimers from higher plants for a parallel estimation of particle size, fluorescence, and antenna cluster homogeneity in a single measurement. FCS revealed that, below detergent critical micelle concentration, low pH promoted the formation of large protein oligomers of sizes up to micrometers, and therefore is apparently incompatible with thylakoid membranes. In contrast, LHCII clusters formed at high pH were smaller and homogenous, and yet still capable of efficient quenching. The results altogether set the physiological validity limits of in vitro quenching experiments. Our data also support the idea that the small, moderately quenching LHCII oligomers found at high pH could be relevant with respect to non-photochemical quenching in vivo.
- Klíčová slova
- antenna proteins, detergent critical micelle concentration, fluorescence correlation spectroscopy, non-photochemical quenching, photoprotection, photosynthesis, protein oligomerization,
- MeSH
- chlorofyl chemie genetika účinky záření MeSH
- fluorescence MeSH
- fluorescenční spektrometrie MeSH
- fotosyntéza genetika MeSH
- fotosystém II - proteinový komplex genetika účinky záření MeSH
- fototrofní procesy genetika MeSH
- homeodoménový protein Antennapedia chemie genetika MeSH
- koncentrace vodíkových iontů MeSH
- proteinové agregáty genetika MeSH
- shluková analýza MeSH
- světlo škodlivé účinky MeSH
- světlosběrné proteinové komplexy chemie genetika MeSH
- tylakoidy chemie genetika účinky záření MeSH
- zeaxanthiny genetika MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chlorofyl MeSH
- fotosystém II - proteinový komplex MeSH
- homeodoménový protein Antennapedia MeSH
- proteinové agregáty MeSH
- světlosběrné proteinové komplexy MeSH
- zeaxanthiny MeSH
The anoxygenic phototrophic bacteria (APB) are an active component of aquatic microbial communities. While DNA-based studies have delivered a detailed picture of APB diversity, they cannot provide any information on the activity of individual species. Therefore, we focused on the expression of a photosynthetic gene by APB communities in two freshwater lakes (Cep lake and the Římov Reservoir) in the Czech Republic. First, we analyzed expression levels of pufM during the diel cycle using RT-qPCR. The transcription underwent a strong diel cycle and was inhibited during the day in both lakes. Then, we compared DNA- (total) and RNA-based (active) community composition by sequencing pufM amplicon libraries. We observed large differences in expression activity among different APB phylogroups. While the total APB community in the Římov Reservoir was dominated by Betaproteobacteria, Alphaproteobacteria prevailed in the active library. A different situation was encountered in the oligotrophic lake Cep where Betaproteobacteria (order Burkholderiales) dominated both the DNA and RNA libraries. Interestingly, in Cep lake we found smaller amounts of highly active uncultured phototrophic Chloroflexi, as well as phototrophic Gemmatimonadetes. Despite the large diversity of APB communities, light repression of pufM expression seems to be a common feature of all aerobic APB present in the studied lakes.
- MeSH
- Alphaproteobacteria izolace a purifikace fyziologie účinky záření MeSH
- bakteriální proteiny genetika metabolismus MeSH
- Betaproteobacteria izolace a purifikace fyziologie účinky záření MeSH
- DNA bakterií genetika izolace a purifikace MeSH
- fotoperioda * MeSH
- fotosyntetické reakční centrum - proteinové komplexy genetika metabolismus MeSH
- fototrofní procesy genetika účinky záření MeSH
- fylogeneze MeSH
- jezera mikrobiologie MeSH
- mikrobiota fyziologie účinky záření MeSH
- regulace genové exprese u bakterií fyziologie účinky záření MeSH
- světlo škodlivé účinky MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
- Názvy látek
- bakteriální proteiny MeSH
- DNA bakterií MeSH
- fotosyntetické reakční centrum - proteinové komplexy MeSH
- PufM protein, Bacteria MeSH Prohlížeč
Phototrophic microorganisms are promising resources for green biotechnology. Compared to heterotrophic microorganisms, however, the cellular economy of phototrophic growth is still insufficiently understood. We provide a quantitative analysis of light-limited, light-saturated, and light-inhibited growth of the cyanobacterium Synechocystis sp. PCC 6803 using a reproducible cultivation setup. We report key physiological parameters, including growth rate, cell size, and photosynthetic activity over a wide range of light intensities. Intracellular proteins were quantified to monitor proteome allocation as a function of growth rate. Among other physiological acclimations, we identify an upregulation of the translational machinery and downregulation of light harvesting components with increasing light intensity and growth rate. The resulting growth laws are discussed in the context of a coarse-grained model of phototrophic growth and available data obtained by a comprehensive literature search. Our insights into quantitative aspects of cyanobacterial acclimations to different growth rates have implications to understand and optimize photosynthetic productivity.
- Klíčová slova
- computational biology, growth model, infectious disease, light limitation, microbiology, photoinhibition, phototrophic growth laws, proteome allocation, resource allocation, systems biology,
- MeSH
- biotechnologie MeSH
- fotosyntéza genetika MeSH
- fototrofní procesy genetika MeSH
- proteom genetika MeSH
- sinice genetika růst a vývoj metabolismus MeSH
- světlo MeSH
- Synechocystis genetika růst a vývoj MeSH
- velikost buňky MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- proteom MeSH
