purple bacteria
| Noun | 1. | purple bacteria - free-living Gram-negative pink to purplish-brown bacteria containing bacteriochlorophyll |
| 单词 | purple bacteria | |||
| 释义 | purple bacteria
Purple Bacteriapurple bacteria[′pər·pəl bak′tir·ē·ə]Purple Bacteriaphotosynthesizing bacteria living in fresh or salt water. The bacteria contain red pigments, or caro-tenoids, which give colonies of the bacteria or accumulations of bacterial cells a dark red coloration. Carotenoids absorb energy (from the blue and green bands of the spectrum that penetrate the water to great depths) and transfer it to the bacteriochloro-phyll. Unlike green plants, sulfureous purple bacteria use hydrogen sulfide rather than water as a hydrogen donor, whereas nonsulfureous purple bacteria use organic substances. Molecular oxygen does not form during photosynthesis. purple bacteriapurple bacteriapurple bacteria (Proteobacteria)a PHYLUM (potentially of KINGDOM status) within the DOMAIN BACTERIA. see CLASSIFICATION. The purple bacteria include most of the Gram-negative bacteria (see GRAM'S STAIN), encompassing both photosynthetic and non-photosynthetic species. The photosynthetic bacteria are generally ANAEROBES (some are FACULTATIVE, others OBLIGATE). They contain BACTERIOCHLOROPHYLL and the purple PROTEIN bacteriorhodopsin. PHOTOSYNTHESIS is ANOXYGENIC. The purple sulphur photosynthetic bacteria use sulphur compounds, such as hydrogen sulphide, instead of water, and produce sulphur granules instead of OXYGEN. The purple non-sulphur photosynthetic bacteria use organic compounds such as acids. Non-photosynthetic bacteria include ENTEROBACTERIA, RHIZOBACTERIA, AGROBACTERIA, RICKETTSIA, MYXOBACTERIA and some of the SULPHATE-REDUCING AND SULPHUR-REDUCING BACTERIA.purple bacteria
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