Abstract
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.
Highlights
Phototrophic purple and green sulfur bacteria have been known for a long time [1].These microorganisms are characterized by using reduced sulfur (S) compounds as electron donors in the process of anoxygenic photosynthesis and are classified into different families based on their morphology, physiological and biochemical characteristics
These granules may be found inside or outside the cell [11]. It should be noted at the outset that most of the following examples of sulfur oxidation in anaerobic sulfur bacteria are described for the species Allochromatium vinosum, whose sulfur metabolism is best studied [27], the reason for choosing the model to conduct the review and to illustrate the information
A very similar grouping of genes can be found in Halorhodospira halophila and most members of the Chlorobiaceae family. These have a cluster of dsrNCABLEFHTMKJOP genes, the only differences from which found in the region found in Allochromatium vinosum are the absence of dsrRS genes and the presence of the dsrT gene (Figure 3)
Summary
Phototrophic purple and green sulfur bacteria have been known for a long time [1] These microorganisms are characterized by using reduced sulfur (S) compounds as electron donors in the process of anoxygenic photosynthesis and are classified into different families based on their morphology, physiological and biochemical characteristics. The aim of this review is to provide a general overview of the literature available on the Chromatiaceae and Chlorobiaceae about their molecular and physiological characteristics, their phylogeny and the associated taxonomy and selected biochemical properties Some of these properties are utilizing reduced sulfur compounds as electron donors for anoxygenic photosynthesis and the structure of their photosynthetic units, composed of light-harvesting complexes and reaction centers
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