Rhodobacter sphaeroides is a kind of purple bacterium; a group of bacteria that can obtain energy through photosynthesis. Its best growth conditions are anaerobicphototrophy and aerobic chemoheterotrophy in the absence of light. R. sphaeroides is also able to fix nitrogen. It is remarkably metabolically diverse, as it is able to grow heterotrophically via fermentation and aerobic and anaerobic respiration. Rhodbacter sphaeroides has been isolated from deep lakes and stagnant waters. Rhodbacter sphaeroides is one of the most pivotal organisms in the study of bacterial photosynthesis. It requires no unusual conditions for growth and is incredibly efficient. The regulation of its photosynthetic machinery is of great interest to researchers, as R. sphaeroides has an intricate system for sensing O2 tensions. Also, when exposed to a reduction in the partial pressure of oxygen, R. sphaeroides develops invaginations in its cellular membrane. The photosynthetic apparatus is housed in these invaginations. These invaginations are also known as chromatophores. The genome of R. sphaeroides is also somewhat intriguing. It has two chromosomes, one of 3 Mb and one of 900 Kb, and five naturally occurring plasmids. Many genes are duplicated between the two chromosomes but appear to be differentially regulated. Moreover, many of the open reading frames on CII seem to code for proteins of unknown function. When genes of unknown function on CII are disrupted, many types of auxotrophy result, emphasizing that the CII is not merely a truncated version of CI.
Small non-coding RNA
s have been identified as components of many regulatory networks. Twenty sRNAs were experimentally identified in Rhodbacter spheroids, and the abundant ones were shown to be affected by singlet oxygen exposure. 1O2 which generates photooxidative stress, is made by bacteriochlorophyll upon exposure to oxygen and light. One of the 1O2 induced sRNAs SorY was shown to be induced under several stress conditions and conferred resistance against 1O2 by affecting a metabolite transporter. SorX is the second 1O2 induced sRNA that counteracts oxidative stress by targeting mRNA for a transporter. It also has an impact on resistance against organic hydroperoxides. A cluster of four homologous sRNAs called CcsR for conserved CCUCCUCCC motif stress-induced RNA has been shown to play a role in photo-oxidative stress resistance as well. PcrZ identified in R. sphaeroides, is a trans-acting sRNA which counteracts the redox-dependent induction of photosynthesis genes, mediated by protein regulators.
