Marine ecosystems bacteria

Study of metabolic capabilities of numerically dominant components of marine ecosystems have been hampered by low culturability of these taxa. Early work showed that bacteria could be serially diluted and grown in filtered seawater in lab... 

In retrospect the Fasham et al. (1990) model stands out for two primary reasons. Firsdy, it was one of the first N-based marine ecosystem models that included exphcit compartments for DON and bacteria. Secondly, and perhaps even more importantly, the model s source code was open , i.e., the code was readily available to any one who wanted it. As a result of the latter, the Fasham et al. (1990) model was subsequently applied to a wide variety of modeling problems by numerous... 

Within this diverse group of organisms, three basic evolutionary lineages are discernable (Delwiche, 2000). The first contains all prokaryotic oxygenic phytoplankton, which belong to one class of bacteria, namely, the cyanobacteria. Cyanobacteria are the only known oxygenic photoautotrophs that existed prior to —2.5 Gyr BP (Ga) (Lipps, 1993 Summons et al., 1999). These prokaryotes numerically dominate the photoautotrophic community in contemporary marine ecosystems and their continued success bespeaks an extraordinary adaptive capacity. At any moment in time, there are —10 cyanobacterial cells in the contemporary oceans. To put that into perspective, the number of cyanobacterial cells in the oceans is two orders of magnitude more than all the stars in the sky. 

Sulfide methylation reactions couple dissimilatory sulfate reduction to DMS production and determine the rates of DMS emission in freshwater wetlands. This process involves acetogenic bacteria, some of which degrade aromatic acids to acetone. In soils, freshwater, and marine ecosystems a wide diversity of other anaerobic and aerobic bacteria can contribute to sulfur gas production. In addition, diverse aerobes (e.g. methylotrophs and sulfate oxidizers) and anaerobes (e.g. methanogenes) consume S gas, thereby regulating fluxes in the atmosphere-biosphere system. 

Fenchel, T. (1984) Suspended marine bacteria as food source, in Flows of energy and materials in marine ecosystems (ed. MJ.R. Fasham), Plenum Press, pp. 301—315. 

Bacteria only assimilate dissolved substrates solid substrates are first hydrolysed by extracellular enzymes before being assimilated. Degradation of detritus starts with hydrolytic cleavage of the particulate material into small molecules which can be assimilated by the bacteria. The end-products of extracellular hydrolysis are most amino acids, mono- and disaccharides, and long-chain fatty acids. In aerobic environments these are taken up directly by heterotrophic bacteria, and further metabolism is intracellular. A variable fraction of the detritus in marine ecosystems is never completely remineralised, but accumulates mainly within the anoxic environment, and is gradually transformed into organic complexes refractory to microbial attack (Fenchel and Jorgensen, 1977). 

It has been found over the last few years that there are marine ecosystems that depend on the existence of methane hydrates. There are certain methane-consuming archaea and bacteria associated with methane hydrate deposits in temperature and pressure regions where the hydrate is close to its decomposition threshold.In one system studied, the archaea interact symbiotically with sulfate-reducing bacteria, with the net result that methane is oxidized and sulfate is reduced ... 

In anaerobic environment (e. g., anoxic water basins, sediments of wetlands, lakes, coastal marine ecosystems) sulfur bacteria reduee sulfate to support respiratory metabolism, using sulfate as a terminal eleetron aeeeptor instead of molecular oxygen dissimilatory sulfate reduction). This proeess is the major pathway for H2S... 

More than 70% of the planet is covered by marine ecosystems which contain many marine microorganisms like marine algae, fungi, actinomycetes, bacteria, etc. (Lam, 2006). Marine actinomycetes were one of the valuable prokaryotes in the biotechnology field and they were also used as secondary metabolites for the formation of nanoparticles (Berdy, 2005) and also antibiotics (Magarvey et al., 2004),... 

Tropical mangrove and marine ecosystems from India have been screened for promising bacteria, that have the capability of accumulating high amounts of PHA (25). From 866 bacterial cultures isolated from this region, 337 cultures were scored positive for the PHA production. Amongst these isolates, seven cultures accumulated more than 1 gl in the culture broth. The thin layer chromatograms of the methyl esters of PHA from the seven cultures showed varied profiles. The sediment samples also showed the presence of PHA with five different monomeric units. 

Students at Harvey Mudd College monitor a saltwater aquarium to study the chemistry of a marine ecosystem. When fish and food are introduced into the aquarium on day 0 in panel a, organic compounds are metabolized to produce NH3. Anunonia is toxic to marine animals when the level exceeds 1 ppm but, fortunately, it is removed by Nitrosomonas bacteria, which colonize the aquarium filter and oxidize NH3 to nitrite (NO2). Alas, NO2 is also toxic at levels above 1 ppm, but it is further oxidized to nitrate (NO J) by a second colonization of Nitrobacter bacteria. The natural process of oxidation of NH3 to NO2 and NOJ is called nitrification. 

There are several reports regarding the novelty of exopolysaccharides extracted from marine bacteria and its pharmaceutical applications. Applicability and acceptability of exopolysaccharides in pharmaceutical industries has now opened a new avenue for the research to utilize novel bacteria that inhabit unexplored marine ecosystems. Microbial exopolysaccharides are constantly evolving, and advancement in biological techniques is required for its in vitro production. The main challenges for the commercialization of new microbial exopolysaccharides are the identification (of both strain... 

In Europe the Baltic Sea, which receives almost 1.5 Mt N annually from agricultural runoff and atmospheric deposition, has been one of the most noticeably eutro-phied marine ecosystems. In many places the hypoxic, or outright anoxic, conditions of the sea s bottom sediments are attested to by the presence of extensive mats of Beggiatoa, bacteria that reduce CO2 and produce sulfates in the absence of oxygen. Appreciable eutrophication has also been observed in the Black, Mediterranean, and North Seas. 

It has been shown that a combination of photolytic and biotic reactions can result in enhanced degradation of xenobiotics in municipal treatment systems, for example, of chlorophenols (Miller et al. 1988a) and benzo[a]pyrene (Miller et al. 1988b). Two examples illustrate the success of a combination of microbial and photochemical reactions in accomplishing the degradation of widely different xenobiotics in natural ecosystems. Both of them involved marine bacteria, and it therefore seems plausible to assume that such processes might be especially important in warm-water marine enviromnents. 

Organisms in natural ecosystems may not be actively dividing but may, nonetheless, be metabolically active. This may be particularly important for ultramicro marine bacteria in their natural habitat. 

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