Photoautotrophs

Photoautotrophs CO2 Light H2O, H2S, S, other inorganic compounds Green plants, algae, cyanobacteria, photosynthetic bacteria... 

Photoautotrophic organisms, such as algae, cyanobacteria, and plants, all contain chlorophyll a and obtain energy by a process known as oxygenic photosynthesis. The overall chemical reaction of this process is ... 

Other roles for noxious metabolites produced by certain phytoplankton species include mediation of allelopathic interactions [47]. Allelopathy covers biochemical interactions among different primary producers or between primary producers and microorganisms. These can provide an advantage for the producer in the competition among different photoautotrophs for resources. Although not directly involved in chemical defense, allelopathic metabolites can affect the dominance and succession of species in phytoplankton therefore they are crucial for understanding plankton composition. In contrast to the fresh water environment, the location of many studies on the role of allelopathic interactions, which have identified active compounds [47], only few studies have addressed this topic in the marine environment. 

Prokaryotes Autotrophs Chemoautotrophs Photoautotrophs Aerobes Energy from energised minerals Energy from oxidised sources, Fe3+, S()42, NO s Energy from light, Mg, Mn Tolerate and use 02 from moderate to high atmospheric levels Use of Mg2+, Fe2+, Mo(W)... 

T. roseopersicina needs so many distinct hydrogenases. Our working hypothesis links this abundance of various NiFe hydrogenases to the fact that this bacterium should be able to perform various metabolic activities (photoautotrophic, photoheterotrophic, heterotrophic metabolism) in order to survive in its natural habitat [Imhoff, 2001]). Having numerous hydrogenases at hand increases the chances of survival for the bacterium and increases our chances to understand basic phenomena of hydrogenase catalysis. 

PS1 The PS 1-prep, introduced in this communication is the first reported with a polyhistidine tag fused to the N-terminus of the PsaF subunit. This construct was possible due to the fact that cyanobacterial PsaF-deletion mutants show no impact on photoautotrophic growth - in contrast to Chlamydomonas reinhardtii, where inactivation of PsaF results in a severe reduction of electron transfer from plastocyanin to PS 1 [Hippier et al. 1997], Also, the N-terminus of the F-subunit which was decorated by the tag is located towards the lumen side which enables an attachment of the isolated PS1 with the lumen-exposed /donor-side to the electrode surface in our hydrogen-producing device. 

The commercial availability of certain toxin standards has allowed researchers to examine the physiological mechanisms of allelopathy by cyanobacteria. The best known examples are from studies on microcystins, which affect plants and aquatic algae by interfering with protein phosphatases in a manner similar to their effect on vertebrate enzymes (Babica et al. 2006). However, there is evidence that microcystins can also promote the formation of reactive oxygen species (ROS) in photoautotrophs, which can cause extensive damage to cellular membranes and enzymes (Babica et al. 2006 Leflaive and Ten-Hage 2007). 

Neurotoxins, such as saxitoxin and anatoxin-a, have been implicated in mediating competitive interactions between toxic cyanobacteria and other photoautotrophs, but few studies have explicitly examined the allelopathic effects of these compounds (e g., Kearns and Hunter 2001). Although it is reasonable to assume that these compounds bind to algal and cyanobacterial sodium channels in a similar fashion as in vertebrate neurons, support for this hypothesis is currently lacking. 

One role of cyanobacterial allelochemicals may be to alter the motility and distribution of competing photoautotrophs. In a recent study, Kearns and Hunter (2001) examined the effects of toxic metabolites from the filamentous cyanobacterium A. flos-aquae on a unicellular phytoplankton species, Chlamydomonas rein-hardtii. A. flos-aquae synthesizes both microcystins as well as anatoxins, providing the authors with an ecologically relevant opportunity to assess the individual and combinatorial effects of these toxins on an alga. 

Among freshwater macroalgae, species of Chara have most frequently been shown to have negative chemically mediated effects upon other aquatic photoautotrophs (Gross 2003). These algae often have a strong odor associated with them, resulting... 

Cultures of S. obliquus can easily be grown photoautotrophically in two-tier flasks in an inorganic medium. A stepwise replacement of H20 by 2H20 leads to deuterated cultures, and a replacement of C02 (the sole carbon source) by 13C02 and/or the replacement of... 

M. Estrada, P. Henriksen, J.M. Gasol, E.O. Casamayor and C. Pedros-Alio, Diversity of planktonic photoautotrophic microorganisms along a salinity gradient as depicted by microscopy, flow cytometry, pigment analysis and DNA-based methods. FEMS Microbiol. Ecol. 49 (2004) 281-293. 

Chlorophyll a (Chi a) functions as the primary light harvesting pigment in marine oxygenic phototrophs. Even though the C Chl a ratio of photoautotrophic cells varies considerably as a function of environmental conditions and growth rate (Laws et al., 1983), measurements of Chi a have been used extensively to estimate the biomass of photoautotrophic microorganisms in the sea. 

C2g isoprenoids Phytol All frans-retinal Photoautotrophs Proteobacteria... 

Photoautotrophic Mode of nutrition based on the use of solar energy to synthesize organic compounds. 

Johnson CM, Beard BL, Albarede E (2004b) Overview and general concepts. Rev Mineral Geochem 55 1-24 Kalinowski BE, Liermann LJ, Brantley SL, Barnes A, Pantano CG (2000) X-ray photoelectron evidence for bacteria-enhanced dissolution of hornblende. Geochim Cosmochim Acta 64 1331-1343 Kappler A, Newman DK (2004) formation of Iron(III)-minerals by Iron(II)-oxidizing photoautotrophic bacteria. Geochim Cosmochim Acta 68 1217-1226... 

These estimates are somewhat different from those in Figures 25.1 and 25.2 Phytopiankton biomass inciudes bacteriai photoautotrophs. 

The inefficiency of microbial heterotrophy does have a side benefit as it enhances nutrient remineralization rates. This serves to increase the availability of inorganic nitrogen and phosphorus for the photoautotrophs. The multiple roles of bacteria in the marine food web were shown in Figure 23.2, with the component of the food web controlled by the algal herbivores depicted on the left side and the microbial loop on the right. The viral shunt acts on both pathways. 

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