Aerobic anoxygenic photosynthetic bacteria with zinc-bacteriochlorophyll.

Abstract

IntroductionChlorophylls (Chls) and bacteriochlorophylls (BChls) are porphyrin derivatives chelated with magnesium, and represent a class of lipophilic pigments involved in natural photosynthesis. There has been no rational explanation for why extant phototrophic organisms have used Mg exclusively as the central metal with which the chlorophyllous pigments are complexed. Apart from this question, phototrophic organisms that use Chls or BChls containing metals other than Mg were unknown for a long time. Recently, this common understanding of natural photosynthesis was unexpectedly modified by the new finding that a novel purple pigment, zinc-chelated-BChl (Zn-BChl) (for abbreviations, see Takaichi et al. (1999)), was discovered in a specific group of obligately aerobic bacteria (Hiraishi et al., 1998;Wakao et al., 1996Wakao et al., , 1999.It has been satisfactorily demonstrated that BChls are present not only in facultatively and obligately anaerobic anoxygenic phototrophic bacteria but also in large numbers of species of obligately aerobic bacteria Naturally occurring chlorophyllous pigments, which function as the cofactor in the early photochemical reaction of photosynthesis, have been proven beyond question to be magnesium-complexed porphyrin derivatives. Phototrophic organisms that use (bacterio)chlorophylls ([B]Chls)containing metals other than Mg were unknown for a long time. This common knowledge of natural photosynthesis has recently been modified by the striking finding that a novel purple pigment, zinc-chelated-BChl (Zn-BChl) a, is present as the major and functional pigment in species of the genus Acidiphilium. Acidiphilium species are obligately acidophilic chemoorganotrophic bacteria that grow and produce photopigments only under aerobic conditions. Although the mechanism of photosynthesis with Zn-BChl a in Acidiphilium species is similar to that seen in common purple bacteria, some characteristic photosynthetic features of the acidophilic bacteria are also found. The discovery of natural photosynthesis with Zn-BChl has not only provided a new insight into our understanding of bacterial photosynthesis but also raised some interesting questions to be clarified. The major questions are why the acidophilic bacteria have selected ZnBChl for their photosynthesis and how they synthesize Zn-BChl and express photosynthetic activity with it in their natural habitats. In this article we review the current knowledge of the biology of Acidiphilium as aerobic photosynthetic bacteria with Zn-BChl a and discuss the interesting topics noted above.

Reclassification of Methylobacterium chloromethanicum and Methylobacterium dichloromethanicum as later subjective synonyms of Methylobacterium extorquens and of Methylobacterium lusitanum as a later subjective synonym of Methylobacterium rhodesianum

“…They proposed the new species Methylobacterium rhodinum, Methylobacterium radiotolerans and Methylobacterium mesophilicum, which were methane-non-utilizing organisms, and amended the description of the genus Methylobacterium . Methylobacterium strains produce carotenoid pigment and bacteriochlorophyll in their cells, and they belong to a group of aerobic bacteriochlorophyll-containing (ABC) bacteria (Hiraishi and Shimada, 2001). Currently, the genus Methylobacterium consists of 14 valid species, Methylobacterium extorquens (Bousfield and Green, 1985), Methylobacterium rhodesianum, Methylobacterium zatmanii and Methylobacterium fujisawaense (Green et al, 1988), Methylobacterium aminovorans (Urakami et al, 1993), Methylobacterium thiocyanatum (Wood et al, 1998), Methylobacterium dichloromethanicum (Doronina et al, 2000), Methylobacterium chloromethanicum (McDonald et al, 2001), Methylobacterium suomiense, and Methylobacterium lusitanum (Doronina et al, 2002).…”

Phylogenetic Study of Methanol Oxidizers from Chilika-Lake Sediments Using Genomic and Metagenomic Approaches

“…However, a few (viz., CS3, CS15, CS8; Table 2) did not exhibit such amplification but still could grow on agar plates even after several streaks. The genus Methylobacterium, a pink pigmented facultative methylotroph follows Serine pathway to metabolize formaldehyde [41], also reported from sea water [45], was dominant in the explored diverse methylotroph communities.…”

“…Methylotrophs are distributed in diverse environments from freshwater Lake [5], deep-sea sediments [9], hypersaline lake [24], chlorinated environments [41], plant phyllosphere [42] to hot water effluent [43], suggesting their ubiquity. Present study focused on the aerobic methylotrophs covering 1,100 km 2 of the Chilika Lake sediments through established molecular markers (such as the functional gene mxaF and phylogenetic 16S rRNA gene probes) which demonstrated the presence of phylogenetically diverse aerobic methylotrophs.…”

“…The halotolerance ability of the representative isolates was studied. Methylobacterium aerobically produces carotenoid pigment and bacteriochlorophyll A indicating that their ability to acquire ATP helps them to survive even in carbon deprivation [41]. Two Methylobacterium sp.…”

Photochemical Transformations Involving Porphyrins and Phthalocyanines

“…These compounds are derived from chl and then processed by the plant or animal. Photosynthetic organisms that utilize chls or bchls containing metals other than Mg were unknown for a long time (Hiraishi and Shimada 2001). Past years have seen increasing evidence that both Mg and Zn chlorophylls do exist in nature.…”