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  • Bacteriochlorophyll  (3)
  • Blue light response  (1)
  • 1
    Electronic Resource
    Electronic Resource
    A phototrophic gliding filamentous bacterium of hot springs, Chloroflexus aurantiacus, gen. and sp. nov. (1974)
    Springer
    Archives of microbiology 100 (1974), S. 5-24 
    Details
    ISSN: 1432-072X
    Keywords: Chloroflexus ; Thermophilic ; Photosynthetic Bacterium ; Filamentous ; Gliding ; Bacteriochlorophyll ; Chlorobium Vesicles ; Photoheterotrophic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chloroflexus aurantiacus, gen. and sp. n., is a filamentous phototrophic bacterium of hot springs. On an agar surface, holotype strain J-10-fl glides at 0.01–0.04 μm/sec. The filaments are 0.6–0.7 μm in width and indeterminate in length. Pigments include bacteriochlorophyll c and bacteriochlorophyll a (identified by spectrophotometry) in addition to β and γ-carotene and glycosides of the latter. Chlorobium vesicles are present. Photoheterotrophic growth occurs under anaerobic conditions. Aerobic chemoheterotrophic growth also occurs in darkness or light. Bacteriochlorophyll syntheses cease under aerobic conditions but some types of carotenoids continue to be made. The filament coloration is orange under all except anaerobic conditions in low light intensity where it is dull green. The pH optimum is near 8, the temperature optimum between 52° and 60°C. The DNA base composition for strain J-10-fl is 54.9 ± 1.0 moles % guanine + cytosine. Chloroflexus is unique in that there have been no previous reports of filamentous or gliding phototrophic bacteria. The combinations of bacteriochlorophylls a and c and the presence of chlorobium vesicles in a photoheterotroph and in an organism capable of aerobic growth are also unique. This metabolically versatile organism extends the taxonomic and phylogenetic limits of the “green line” of phototrophic bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446302
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  • 2
    Electronic Resource
    Electronic Resource
    Studies of pigments and growth in Chloroflexus aurantiacus, a phototrophic filamentous bacterium (1974)
    Springer
    Archives of microbiology 100 (1974), S. 283-305 
    Details
    ISSN: 1432-072X
    Keywords: Chloroflexus ; Thermophilic ; Photosynthetic Bacterium ; Bacteriochlorophyll ; Pigment Regulation ; Respiration in Light ; Carotenoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The chlorophyll pigments of Chloroflexus aurantiacus were separated by column chromatography on powdered sugar and were identified by spectrophotometry in various solvents as BChl a and BChl c (chlorobium chlorophyll 660). The bacteriopheophytins were also prepared and characterized-spectrophotometrically. The identity of the BChl a is tentative because of its anomalous phase test behavior and because of changes in its absorption spectrum observed under different conditions of preparation. 2. Growth rates of Chloroflexus at 55°C and synthesis of the 2 chlorophylls were compared in cells growing under anaerobic conditions at different light intensities. Growth rates increased with increasing light intensity to a saturation level of about 0.30 doublings/hr at 20 000 lux and above during the second exponential phase of growth. The rate of the first exponential phase continued to increase, at least up to 50 000 lux. The specific content of both chlorophylls decreased with increasing light intensity but to different extents. A linear relationship between specific chlorophyll content and growth rate for either chlorophyll was only observed over a limited range of growth rates. The ratio of BChl c/BChl a decreased with increasing light intensity. The greatest change occurred between 300 and 5000 lux. The differential responses of BChl c and BChl a to light intensity were also demonstrated by shifting highly pigmented cells (grown at low light intensity) to high light intensity. In these cases different rates of synthesis of the 2 pigments followed initial adjustments. Carotenoid synthesis did not decrease with increasing light intensity under anaerobic conditions. 3. Chlorophyll synthesis was suppressed under fully aerobic conditions in dark-ness and light. In either case the pigments were diluted out by continued cell growth. At least 1 carotenoid pigment, however, was synthesized under aerobic conditions. Other carotenoids characteristic of anaerobic growth were not observed. 4. The chemoheterotrophic aerobic growth rate at 55°C in darkness (0.14 to 0.22 d/hr) was less than the maximum second phase phototrophic rate under anaerobic conditions (0.30 d/hr). Aerobic growth rate in the light was the same as in darkness if chlorophylls were lacking, but was enhanced if these pigments were still present. The oxygen consumption rate was partially suppressed in the light only when chlorophylls were present in the cells. 5. A light-minus-dark diffrence spectrum revealed the presence of a light-induced reversible decrease in absorbance of BChl a with a maximum effect at 860 nm, tentatively identifying a reaction center complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446324
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  • 3
    Electronic Resource
    Electronic Resource
    A thermophilic green sulfur bacterium from New Zealand hot springs, Chlorobium tepidum sp. nov. (1991)
    Springer
    Archives of microbiology 156 (1991), S. 81-90 
    Details
    ISSN: 1432-072X
    Keywords: Chlorobium tepidum ; Photosynthesis ; Green sulfur bacteria ; Chlorosomes ; Bacteriochlorophyll ; Thermophily ; Hot springs ; 16S rRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Thermophilic green sulfur bacteria of the genus Chlorobium were isolated from certain acidic high sulfide New Zealand hot springs. Cells were Gram-negative nonmotile rods of variable length and contained bacteriochlorophyll c and chlorosomes. Cultures of thermophilic chlorobia grew only under anaerobic, phototrophic conditions, either photoautotrophically or photoheterotrophically. The optimum growth temperature for the strains of thermophilic green sulfur bacteria isolated was 47–48°C with generation times of about 2 h being observed. The upper temperature limit for growth was about 52°C. Thiosulfate was a major electron donor for photoautotrophic growth while sulfide alone was only poorly used. N2 fixation was observed at 48°C and cell suspensions readily reduced acetylene to ethylene. The G+C content of DNA from strains of thermophilic chlorobia was 56.5–58.2 mol% and the organisms positioned phylogenetically within the green sulfur bacterial branch of the domain Bacteria. The new phototrophs are described as a new species of the genus Chlorobium, Chlorobium tepidum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00290978
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  • 4
    Electronic Resource
    Electronic Resource
    Light responses ofBeggiatoa (1982)
    Springer
    Archives of microbiology 131 (1982), S. 146-155 
    Details
    ISSN: 1432-072X
    Keywords: Beggiatoa ; Blue light response ; Colorless sulfur bacteria ; Step-up phobic light response ; Weber Law response ; Diel vertical migration ; Receptor pigment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies on nativeBeggiatoa demonstrated diel vertical migration into, and out of, sediments at the bottom of warm spring pools. Laboratory experiments withBeggiatoa in natural sediments suggested that high light was the cause of the downward movement. The nature of this presumed photomotion was clarified by microscopic observation of individual filaments of nativeBeggiatoa at light/dark boundaries where the light was varied in intensity and quality. Using “white light”, a negative photo-response was demonstrated, and a dose-response curve was constructed which indicates an increasing response to light over three orders of magnitude of intensity. A coarse action spectrum implicated a pigment with a peak in the blue region as the receptor. Pure culture studies showed the negative response to be a step-up phobic one. The light intensity increase necessary to invoke reversals was a smaller percentage of the initial intensity for higher initial intensities. The light intensity levels and gradient strengths necessary to evoke reversals in single filaments were consistent with the hypothesis that the step-up response accounts for the disappearance in the field. This response has adaptive significance since full sunlight was completely inhibitory toBeggiatoa growth, even when filaments were aggregated in tufts. Dilute suspensions were also inhibited by as little as 5000 lux (fluorescent lamps).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01053997
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