Filamentous photosynthetic bacteria

Filamentous photosynthetic bacteria Chloroflexus CMoronema Heliothrix Oscillochloris Filamentous rods... 

The rRNA catalogs for the various eubacterial phyla do not permit us to infer a branching order, because the 5 8 (association coefficient) values between the major branches are too low to be significant. For example, between members of the green sulfur bacteria and members of the filamentous photosynthetic bacteria 5 8 values range from 0.12 to 0.20 [111]. These values are too low to establish branching orders with respect to other phyla , for example Escherichia coli (purple bacteria and relatives, 5 8 = 0.17-0.28) and Bacillus pumilus (gram-positive bacteria, 5 8 = 0.18-0.24). As shown in Fig. 1, the various phyla disappear into... 

As in the case of the purple photosynthetic bacteria, the more stable electron acceptor of green filamentous bacteria was first detected using instrumentation with millisecond-time resolution and so the rise and decay kinetics of any earlier electron acceptor(s) would be too fast to be detected. The detection of any earlier electron acceptor would require greater time resolution, such as afforded by picosecond spectroscopy. As a framework for further discussion we write the sequence of the primary photochemical and electron-transfer reactions in green filamentous bacteria as follows ... 

Aerobic bacteria such as Azotobacter vinelandii, Alcaligenes eutrophus, and Nocardia opaca, and facultative anaerobes, such as Escherichia coli and various species of Rhizobium and Bradyrhizobium (the symbionts of leguminous plants), also contain hydrogenase, as do photosynthetic bacteria such as Chromatium vinosum, Rhodobacter capsulatus (formerly Rhodopseudomonas capsulata), and Anabaena variabilis (a filamentous cyanobacterium). The thermophilic hydro-... 

The Chloroflexaceae are green filamentous bacteria. They form a deep division in the eubacterial line and have an interesting combination of the characteristics found in very different and diverse groups of photosynthetic bacteria (Pierson and Castenholz,... 

According to modern taxonomy, four divisions of photosynthetic bacteria are discerned (1) the purple bacteria, the green sulfur bacteria (Chlorobiaceae), the green filamentous (or gliding) bacteria (Chloroflexaceae) and the heliobacteria. This contribution concerns the antenna properties of the last three groups groups which have been studied less extensively than the purple bacteria, but which are not less interesting from the scientific point of view. 

Another nonheme Mn center is believed [172] to be present in photosynthetic green filamentous bacteria. The locus of the Mn ion in these bacteria is similar to that of the nonheme Fe11 in photosynthetic purple bacteria [173], i.e., between two quinones, along the pathway of electron transfer. Since the Fe center of purple bacteria does not seem to be involved directly in the electron transfer process (i.e., is not redox-active), the redox role of the Mn analog remains in question. This Mn may be redox-active, considering that (1) structural differences between the purple and green bacteria photosynthetic apparatus do exist [173] and (2) the green bacteria display different functionalities, such as C02 fixation, which does not occur via the classical Calvin or reverse Krebs cycle [174],... 

All known photosynthetic eubacteria (including cyanobacteria) contain Chi a, BChl g, BChl a or BChl b in their RCs. Chi a is restricted to the cyanobacteria and BChl g to the gram-positive line (as far as we know). As shown in Fig. 5 chlo-rophyllide a and BChl-ide g are isomers of one another [65]. BChl a is found in the RCs of green bacteria, purple bacteria and filamentous bacteria. So far BChl b has been found only in purple bacteria. We have suggested that all photosynthetic eubacteria are descendents of a common ancestor containing Chi a in an RC-1 type RC [112], and we suppose that the gram-positive line of bacteria (BChl g)... 

Photosynthetic eubacteria are classified as filamentous, green sulfur, gram-positive linked, purple, and cyanobacteria. All contain membrane-bound RCs in which (B)Chl serves as the primary electron donor. The RCs may be divided into two main types RC-1, in which the initial electron acceptor is a (B)Chl molecule and the secondary acceptor is an Fe-S center, and RC-2, in which the initial acceptor is a (B)Ph molecule and the secondary acceptor is a quinone. RC-1 centers are found in green sulfur and gram-positive linked bacteria, while RC-2 centers are found in filamentous bacteria and purple bacteria. Cyanobacteria contain both RC-1 and RC-2 centers in which the chlorophyll is Chi a. BChl a is found in filamentous, green sulfur and purple bacteria, while BChl g is characteristic of the grampositive line. BChl b is found in certain purple bacteria instead of BChl a. 

Those photosynthetic eubacteria with RC-2 centers (filamentous and purple bacteria) reduce NAD" for CO2 fixation by reverse electron flow from the quinone pool, whereas the green sulfur bacteria (RC-1 center) reduce ferredoxin and NAD directly from the secondary acceptor (Fe-S center) of the RC. In both cases an external reductant such as H2S is required. The mechanism of NAD reduction in the gram-positive line has not yet been investigated, but H. chlorum is a het-erotroph rather than an autotroph, and may not need to fix CO2. 

Many photosynthetic purple bacteria are closely related phylogenetically to nonphotosynthetic respiring eubacteria. Some photosynthetic eubacteria are autotrophic (e.g. green and purple sulfur bacteria), while others are mainly hetero-trophic (e.g. filamentous bacteria, purple non-sulfur bacteria and H. chlorum). All convert light energy into chemical free energy. 

Interestingly, reaction centers of apparently all photosynthetic organisms may be assigned to one or the other of these two types. For instance, the reaction center of both purple bacteria and the green filamentous bacteria, Chloroflexaceae, and green-plant PS II are of the OQ-type. On the other hand, the green sulfur bacteria, Chlorobiaceae, the Heliobacteria, and photosystem I all have the FeS-type reaction centers. 

Figure 19.4 Cyanobacteria. A colony of the photosynthetic filamentous cyanobacterium Anabaena shown at 450 X magnification. Ancestors of these bacteria are thought to have evolved into present-day chloroplasts. [James W. Richardson/Visuals Unlimited.]... 

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