Open AccessCO 2 assimilation in the chemocline of L ake C adagno is dominated by a few types of phototrophic purple sulfur bacteria
Author(s) -
Storelli Nicola,
Peduzzi Sandro,
Saad Maged M.,
Frigaard NielsUlrik,
Perret Xavier,
Tonolla Mauro
Publication year - 2013
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/1574-6941.12074
Subject(s) - chemocline , phototroph , biology , green sulfur bacteria , photosynthesis , botany , bacteria , darkness , sulfur , population , rhodospirillales , genetics , chemistry , organic chemistry , demography , sociology
L ake C adagno is characterized by a compact chemocline that harbors high concentrations of various phototrophic sulfur bacteria. Four strains representing the numerically most abundant populations in the chemocline were tested in dialysis bags in situ for their ability to fix CO 2 . The purple sulfur bacterium C andidatus ‘Thiodictyon syntrophicum’ strain C ad16 T had the highest CO 2 assimilation rate in the light of the four strains tested and had a high CO 2 assimilation rate even in the dark. The CO 2 assimilation of the population represented by strain C ad16 T was estimated to be up to 25% of the total primary production in the chemocline. Pure cultures of strain C ad16 T exposed to cycles of 12 h of light and 12 h of darkness exhibited the highest CO 2 assimilation during the first 4 h of light. The draft genome sequence of C ad16 T showed the presence of cbbL and cbbM genes, which encode form I and form II of RuBis CO , respectively. Transcription analyses confirmed that, whereas cbbM remained poorly expressed throughout light and dark exposure, cbbL expression varied during the light–dark cycle and was affected by the available carbon sources. Interestingly, the peaks in cbbL expression did not correlate with the peaks in CO 2 assimilation.