scholarly journals Genetic Manipulation of Carotenoid Biosynthesis in the Green Sulfur Bacterium Chlorobium tepidum

2004 ◽  
Vol 186 (16) ◽  
pp. 5210-5220 ◽  
Author(s):  
Niels-Ulrik Frigaard ◽  
Julia A. Maresca ◽  
Colleen E. Yunker ◽  
A. Daniel Jones ◽  
Donald A. Bryant
Keyword(s):  
Genetic Manipulation ◽  
Sequence Similarity ◽  
Carotenoid Biosynthesis ◽  
Green Sulfur Bacteria ◽  
Chlorobium Tepidum ◽  
Sequence Motifs ◽  
Green Sulfur Bacterium ◽  
Sulfur Bacteria ◽  
Carotenoid Composition ◽  
Green Sulfur

ABSTRACT The green sulfur bacterium Chlorobium tepidum is a strict anaerobe and an obligate photoautotroph. On the basis of sequence similarity with known enzymes or sequence motifs, nine open reading frames encoding putative enzymes of carotenoid biosynthesis were identified in the genome sequence of C. tepidum, and all nine genes were inactivated. Analysis of the carotenoid composition in the resulting mutants allowed the genes encoding the following six enzymes to be identified: phytoene synthase (crtB/CT1386), phytoene desaturase (crtP/CT0807), ζ-carotene desaturase (crtQ/CT1414), γ-carotene desaturase (crtU/CT0323), carotenoid 1′,2′-hydratase (crtC/CT0301), and carotenoid cis-trans isomerase (crtH/CT0649). Three mutants (CT0180, CT1357, and CT1416 mutants) did not exhibit a discernible phenotype. The carotenoid biosynthetic pathway in C. tepidum is similar to that in cyanobacteria and plants by converting phytoene into lycopene using two plant-like desaturases (CrtP and CrtQ) and a plant-like cis-trans isomerase (CrtH) and thus differs from the pathway known in all other bacteria. In contrast to the situation in cyanobacteria and plants, the construction of a crtB mutant completely lacking carotenoids demonstrates that carotenoids are not essential for photosynthetic growth of green sulfur bacteria. However, the bacteriochlorophyll a contents of mutants lacking colored carotenoids (crtB, crtP, and crtQ mutants) were decreased from that of the wild type, and these mutants exhibited a significant growth rate defect under all light intensities tested. Therefore, colored carotenoids may have both structural and photoprotection roles in green sulfur bacteria. The ability to manipulate the carotenoid composition so dramatically in C. tepidum offers excellent possibilities for studying the roles of carotenoids in the light-harvesting chlorosome antenna and iron-sulfur-type (photosystem I-like) reaction center. The phylogeny of carotenogenic enzymes in green sulfur bacteria and green filamentous bacteria is also discussed.

scholarly journals Two Genes Encoding New Carotenoid-Modifying Enzymes in the Green Sulfur Bacterium Chlorobium tepidum

2006 ◽  
Vol 188 (17) ◽  
pp. 6217-6223 ◽  
Author(s):  
Julia A. Maresca ◽  
Donald A. Bryant
Keyword(s):  
Green Sulfur Bacteria ◽  
The Other ◽  
Chlorobium Tepidum ◽  
Green Sulfur Bacterium ◽  
Gene Encoding ◽  
Anoxygenic Phototrophs ◽  
Sulfur Bacteria ◽  
Genes Encoding ◽  
Green Sulfur ◽  
Predicted Function

ABSTRACT The green sulfur bacterium Chlorobium tepidum produces chlorobactene as its primary carotenoid. Small amounts of chlorobactene are hydroxylated by the enzyme CrtC and then glucosylated and acylated to produce chlorobactene glucoside laurate. The genes encoding the enzymes responsible for these modifications of chlorobactene, CT1987, and CT0967, have been identified by comparative genomics, and these genes were insertionally inactivated in C. tepidum to verify their predicted function. The gene encoding chlorobactene glucosyltransferase (CT1987) has been named cruC, and the gene encoding chlorobactene lauroyltransferase (CT0967) has been named cruD. Homologs of these genes are found in the genomes of all sequenced green sulfur bacteria and filamentous anoxygenic phototrophs as well as in the genomes of several nonphotosynthetic bacteria that produce similarly modified carotenoids. The other bacteria in which these genes are found are not closely related to green sulfur bacteria or to one another. This suggests that the ability to synthesize modified carotenoids has been a frequently transferred trait.

scholarly journals Physiology and Phylogeny of Green Sulfur Bacteria Forming a Monospecific Phototrophic Assemblage at a Depth of 100 Meters in the Black Sea

2005 ◽  
Vol 71 (12) ◽  
pp. 8049-8060 ◽  
Author(s):  
Ann K. Manske ◽  
Jens Glaeser ◽  
Marcel M. M. Kuypers ◽  
Jörg Overmann
Keyword(s):  
Black Sea ◽  
Sulfide Oxidation ◽  
Green Sulfur Bacteria ◽  
The Black Sea ◽  
Rrna Gene ◽  
Green Sulfur Bacterium ◽  
Sulfur Bacteria ◽  
Light Intensities ◽  
Green Sulfur

ABSTRACT The biomass, phylogenetic composition, and photoautotrophic metabolism of green sulfur bacteria in the Black Sea was assessed in situ and in laboratory enrichments. In the center of the western basin, bacteriochlorophyll e (BChl e) was detected between depths of 90 and 120 m and reached maxima of 54 and 68 ng liter−1. High-pressure liquid chromatography analysis revealed a dominance of farnesyl esters and the presence of four unusual geranyl ester homologs of BChl e. Only traces of BChl e (8 ng liter−1) were found at the northwestern slope of the Black Sea basin, where the chemocline was positioned at a significantly greater depth of 140 m. Stable carbon isotope fractionation values of farnesol indicated an autotrophic growth mode of the green sulfur bacteria. For the first time, light intensities in the Black Sea chemocline were determined employing an integrating quantum meter, which yielded maximum values between 0.0022 and 0.00075 μmol quanta m−2 s−1 at the top of the green sulfur bacterial layer around solar noon in December. These values represent by far the lowest values reported for any habitat of photosynthetic organisms. Only one 16S rRNA gene sequence type was detected in the chemocline using PCR primers specific for green sulfur bacteria. This previously unknown phylotype groups with the marine cluster of the Chlorobiaceae and was successfully enriched in a mineral medium containing sulfide, dithionite, and freshly prepared yeast extract. Under precisely controlled laboratory conditions, the enriched green sulfur bacterium proved to be capable of exploiting light intensities as low as 0.015 μmol quanta m−2 s−1 for photosynthetic 14CO2 fixation. Calculated in situ doubling times of the green sulfur bacterium range between 3.1 and 26 years depending on the season, and anoxygenic photosynthesis contributes only 0.002 to 0.01% to total sulfide oxidation in the chemocline. The stable population of green sulfur bacteria in the Black Sea chemocline thus represents the most extremely low-light-adapted and slowest-growing type of phototroph known to date.

scholarly journals A Green Sulfur Bacterium From Epsomitic Hot Lake, Washington, USA

2020 ◽  
Author(s):  
Michael T. Madigan ◽  
Megan L. Kempher ◽  
Kelly S. Bender ◽  
Deborah O. Jung ◽  
W. Matthew Sattley ◽  
...  
Keyword(s):  
Phylogenetic Analyses ◽  
Late Summer ◽  
Green Sulfur Bacteria ◽  
Hypersaline Lake ◽  
Green Sulfur Bacterium ◽  
Sulfur Bacteria ◽  
Lake Washington ◽  
Pure Cultures ◽  
Green Sulfur ◽  
Anoxic Zones

Hot Lake is a small heliothermal and hypersaline lake in far north-central Washington State (USA) and is limnologically unusual because MgSO4 rather than NaCl is the dominant salt. In late summer, the Hot Lake metalimnion becomes distinctly green from blooms of planktonic phototrophs. In a study undertaken over 60 years ago, these blooms were predicted to include green sulfur bacteria but no cultures were obtained. We sampled Hot Lake and established enrichment cultures for phototrophic sulfur bacteria in MgSO4-rich sulfidic media. Most enrichments turned green or red within two weeks, and from green-colored enrichments, pure cultures of a lobed green sulfur bacterium (Phylum Chlorobi) were isolated. Phylogenetic analyses showed the organism to be a species of the prosthecate green sulfur bacterium Prosthecochloris. Cultures of this Hot Lake phototroph were halophilic and tolerated high levels of sulfide and MgSO4. In addition, unlike all recognized species of Prosthecochloris, the Hot Lake isolates grew at temperatures up to 45°C, indicating an adaptation to the warm summer temperatures of the lake. Photoautotrophy by Hot Lake green sulfur bacteria may contribute dissolved organic matter to anoxic zones of the lake, and their diazotrophic capacity may provide a key source of bioavailable nitrogen, as well.

scholarly journals The bchU Gene of Chlorobium tepidum Encodes the C-20 Methyltransferase in Bacteriochlorophyll c Biosynthesis

2004 ◽  
Vol 186 (9) ◽  
pp. 2558-2566 ◽  
Author(s):  
Julia A. Maresca ◽  
Aline Gomez Maqueo Chew ◽  
Marta Ros Ponsatí ◽  
Niels-Ulrik Frigaard ◽  
John G. Ormerod ◽  
...  
Keyword(s):  
Near Infrared ◽  
Stop Codon ◽  
Green Sulfur Bacteria ◽  
Infrared Light ◽  
Chlorobium Tepidum ◽  
Spontaneous Mutant ◽  
Reading Frame ◽  
Sulfur Bacteria ◽  
Light Intensities ◽  
Green Sulfur

ABSTRACT Bacteriochlorophylls (BChls) c and d, two of the major light-harvesting pigments in photosynthetic green sulfur bacteria, differ only by the presence of a methyl group at the C-20 methine bridge position in BChl c. A gene potentially encoding the C-20 methyltransferase, bchU, was identified by comparative analysis of the Chlorobium tepidum and Chloroflexus aurantiacus genome sequences. Homologs of this gene were amplified and sequenced from Chlorobium phaeobacteroides strain 1549, Chlorobium vibrioforme strain 8327d, and C. vibrioforme strain 8327c, which produce BChls e, d, and c, respectively. A single nucleotide insertion in the bchU gene of C. vibrioforme strain 8327d was found to cause a premature, in-frame stop codon and thus the formation of a truncated, nonfunctional gene product. The spontaneous mutant of this strain that produces BChl c (strain 8327c) has a second frameshift mutation that restores the correct reading frame in bchU. The bchU gene was inactivated in C. tepidum, a BChl c-producing species, and the resulting mutant produced only BChl d. Growth rate measurements showed that BChl c- and d-producing strains of the same organism (C. tepidum or C. vibrioforme) have similar growth rates at high and intermediate light intensities but that strains producing BChl c grow faster than those with BChl d at low light intensities. Thus, the bchU gene encodes the C-20 methyltransferase for BChl c biosynthesis in Chlorobium species, and methylation at the C-20 position to produce BChl c rather than BChl d confers a significant competitive advantage to green sulfur bacteria living at limiting red and near-infrared light intensities.

scholarly journals Ignavibacterium album gen. nov., sp. nov., a moderately thermophilic anaerobic bacterium isolated from microbial mats at a terrestrial hot spring and proposal of Ignavibacteria classis nov., for a novel lineage at the periphery of green sulfur bacteria

2010 ◽  
Vol 60 (6) ◽  
pp. 1376-1382 ◽  
Author(s):  
Takao Iino ◽  
Koji Mori ◽  
Yoshihito Uchino ◽  
Tatsunori Nakagawa ◽  
Shigeaki Harayama ◽  
...  
Keyword(s):  
Microbial Mats ◽  
Hot Spring ◽  
Sequence Similarity ◽  
Green Sulfur Bacteria ◽  
Phylogenetic Position ◽  
Rrna Gene ◽  
Strictly Anaerobic ◽  
Moderately Thermophilic ◽  
Sulfur Bacteria ◽  
Green Sulfur

A moderately thermophilic chemoheterotrophic bacterium, strain Mat9-16T, was isolated from microbial mats developed in hot spring water streams from Yumata, Nagano, Japan. Cells of strain Mat9-16T were strictly anaerobic, Gram-stain-negative, non-sporulating, non-motile and short to long rods (2.0–15.5 μm in length). Strain Mat9-16T grew fermentatively with optimum growth at 45 °C, pH 7.0–7.5 and 1 % NaCl (w/v). Phylogenetic analysis based on the 16S rRNA gene revealed that strain Mat9-16T was affiliated with an uncultivated lineage, and the nearest cultivated neighbours were green sulfur bacteria belonging to the class Chlorobea with 77–83 % sequence similarity. However, strain Mat9-16T could not grow phototrophically and did not possess light-harvesting structures, morphologically and genetically, such as the chlorosomes of green sulfur bacteria. On the basis of phenotypic features and phylogenetic position, a novel genus and species are proposed for strain Mat9-16T, to be named Ignavibacterium album gen. nov., sp. nov. (=NBRC 101810T =DSM 19864T). We also propose to place the cultivated bacterial lineage accommodating the sole representative Mat9-16T in a novel class, Ignavibacteria classis nov. In addition, we present a formal description of the phylum-level taxon ‘Chlorobi’ as Chlorobi phyl. nov.

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