A unique low light adaptation mechanism inRhodobacter azotoformans

Abstract

In this paper, we reported for the first time that Rhodobacter azotoformans was capable of synthesizing a spectral variant of peripheral light-harvesting complex (LH3), besides a high light form (LH2), in response to low light intensity. Carotenoid components in these complexes were analyzed by absorption spectra, high-pressure liquid chromatography and mass spectroscopy analysis. Only spheroidene carotenoid was detected in LH2, while LH3 possessed three kinds of carotenoids, spheroidene, spirilloxanthin, and anhydrorhodovibrin. The spirilloxanthin and anhydrorhodovibrin predominated in LH3 and were rarely found in Rhodobacter species. Carotenoid-to-bacteriochlorophyll energy transfer efficiency in LH3 increased by 4% compared to that in LH2. Raman spectroscopic properties of carotenoids in both complexes supported the view that carotenoids altered their planar configuration to a distorted form by interaction with protein matrix in response to low light conditions. In conclusion, the low light adaptation mechanism of Rba. azotoformans involved regulating the synthesis of LH3 and additional carotenoids as well as the configuration change of incorporated carotenoids.

The Growth‐promoting Mechanism of Unusual Spectroscopic Form of LH2 (LH4) from Rhodopseudomonas palustris CGA009 in Low Light

“…This subsequently affected negatively the cell growth. Niedzwiedzki (2012) studies have shown that the unusually spectral LH3 could efficiently transfer energy from Car to BChl a than that of LH2, which was also supported by our previous study . Although no direct evidence on growth promoting of LH3, it has been agreed that the expression of LH3 would be favorable to cell growth under LL.…”

“…azotoformans and All. vinosum . For LH4, its absorption spectrum and geometric structure have been reported , while there was only computational simulation in its energy efficiency .…”

“…The supernatant was then subjected to gradient ammonium sulfate fractionation from 30% to 80% saturation. Further purification of the PPC complexes was performed by using DEAE anion exchange chromatography on an ÄKTA Purifier chromatography system as previously described .…”

“…Our previous study firstly revealed that Rhodobacter ( Rba .) azotoformans could, respectively, synthesize standard LH2 under high light (HL) and B800‐820 LH2 complex under LL .…”

Genome Sequence of Rhodoferax antarcticus ANT.BRT; A Psychrophilic Purple Nonsulfur Bacterium from an Antarctic Microbial Mat

“…antarcticus synthesizes an LH3 complex [ 3 ]. At least three species of purple bacteria that produce both LH2 and LH3 ( Rhodobacter azotoformans , Phaeospirillum molischianum , and Rhodoblastus acidophilus ) have been shown to exhibit a change in the ratio of peripheral complexes when light intensity or temperature changes [ 27 , 28 , 29 , 30 ]. In these bacteria, low temperatures and/or low light intensity elicit an increase in the expression of LH3 complexes and a decrease in the expression of LH2 complexes.…”