Heterotrophs bacteria

Besides nitrogen fixation, the only other major source of reduced nitrogen is the decomposition of soil or aquatic organic matter. This process is called ammonification. Heterotrophic bacteria are principally responsible for this. These organisms utilize organic compounds from dead plant or animal matter as a carbon source, and leave behind NH3 and NHJ, which can then be recycled by the biosphere. In some instances heterotrophic bacteria may incorporate a complete organic molecule into their own biomass. The majority of the NH3 produced in this way stays within the biosphere however, a small portion of it will be volatilized. In addition to this source, the breakdown of animal excreta also contributes to atmospheric... 

Kjellberg S, M Hermansson, P Marden, GW Jones (1987) The transient phase between growth and nongrowth of heterotrophic bacteria with emphasis on the marine environment. Annu Rev Microbiol 41 25-49. Klump H, J Di Ruggiero, M Kessel, J-B Park, MWW Adams, FT Robb (1992) Glutamate dehydrogenase from the hyperthermophile Pyrococcus furiosus. Thermal denaturation and activation. J Biol Chem 267 22681-22685. 

Arsenite is also an intermediate in the fungal biomethylation of arsenic (Bentley and Chasteen 2002) and oxidation to the less toxic arsenate can be accomplished by heterotrophic bacteria including Alcaligenes faecalis. Exceptionally, arsenite can serve as electron donor for chemolithotrophic growth of an organism designated NT-26 (Santini et al. 2000), and both selenate and arsenate can be involved in dissimilation reactions as alternative electron acceptors. 

Bruns A, H Cypionka, J Overmann (2002) Cyclic AMP and acyl homoserine lactones increase cultivation efficiency of heterotrophic bacteria from the Central Baltic Sea. Appl Environ Microbiol 68 3978-3987. 

In highly saline brines, which were collected from the Vassar Vertz Sand Unit, Pajme County, Oklahoma, diverse populations of anaerobic, heterotrophic bacteria were present. All strains grew in a mineral salts medium containing glucose, yeast extract, and casamino acids in the presence of NaCl concentrations of up to 20% by weight [177],... 

Biofilms are a complex mixture of bacteria, algae and other organisms (Fig. 11). In well-illuminated environments, micro-algae (phytobenthos) make up the largest fraction of the biofilm biomass, which plays a vital role as a primary producer. However, in non-lit environments, heterotrophs (bacteria, protozoa) account for the greatest proportion within the biofilm. The composition and abundance of phytobenthos (periphyton or autotrophic biofilm) have a recognised role by the WFD. 

Jeanthon, C. and D. Prieur. 1990. Susceptibihty to heavy metals and characterization of heterotrophic bacteria isolated from two hydrothermal vent polychaete annelids, Alvinella pompejana and Alvinella caudata. Appl. Environ. Microbiol. 56 3308-3314. 

Sanitary sewer network sanitary sewers—often identified as separate sewers — are developed to collect and transport wastewater from residential areas, commercial areas and industries. The wastewater transported in these sewers typically has a relatively high concentration of biodegradable organic matter and is therefore biologically active. Wastewater in these sewers is, from a process point of view, a mixture of biomass (especially heterotrophic bacteria) and substrate for this biomass. 

In a system defined by wastewater in a sewer network, the heterotrophic bacteria dominate the microbial community, i.e., organic compounds are required as a carbon source. Furthermore, the energy source (electron donor) for the heterotrophs is primarily also organic compounds, i.e., the heterotrophs that dominate wastewater in sewers are chemoheterotrophic (chemoorganotrophic) microorganisms. 

Jones JG, Gardener S, Simon BM. 1984. Reduction of ferric iron by heterotrophic bacteria in lake sediments. J Gen Microbiol 130 45-51. 

Structures of siderophores synthesized by marine heterotrophic bacteria (a) aquacheiins from Halomonas aquamahna, (b) iron binding to muitipie oxygen atoms in an aquacheiin,... 

In addition to serving as the major food source to heterotrophic bacteria, DOM plays an important ecological role in enabling marine organisms to control various aspects of their environment including trophic interrelationships. This is accomplished by the secretion or exudation of specific molecules, called secondary metabolites. These are generally LMW compounds that tend to be species specific in their source and targets. Some act as toxins that repel or kill competitors or predators. As noted earlier, some diatoms... 

During denitrification, nitrate is reduced to N2(g) by heterotrophic bacteria. The stoichiometry for this process was presented in Eq. 8.11 and Table 12.1 for the water column and the sediments, respectively. Denitrification is thought to be performed by fecultative aerobes that switch to nitrate respiration when O2 concentrations are less than 5 p-M (0.1 ml/L). 

Under anaerobic conditions, heterotrophic bacteria will use organic matter as an electron donor to drive the reduction of nitrate to ammonia. This process is called dts-similatory reduction of nitrate to ammonium (DNRA) and appears to be an important sink of nitrate in coastal and estuarine sediments. Similarly, some sedimentary bacteria are probably performing DNRA using sulfide as the electron donor. 

Denitrification The conversion of fixed nitrogen, typically nitrate, into N2 gas. This is achieved by heterotrophic bacteria that use nitrate as an electron acceptor under suboxic and anoxic conditions. 

In wetlands N2 fixation can occur in the water colnmn, in the aerobic water-soil interface, in the anaerobic soil bulk, in the rhizosphere, and on the leaves and stems of plants. Phototrophic bacteria in the water and at the water-soil interface are generally more important than non-photosynthetic, heterotrophic bacteria in the soil and on plant roots (Buresh et al, 1980 Roger 1996). The phototrophs comprise bacteria that are epiphytic on plants and cyanobacteria that are both free-living and epiphytic. A particularly favourable site for cyanobacteria is below the leaf surface of the water fern Azolla, which forms a very efficient symbiosis with the cyanobacterinm Anabaena azollae. This symbiosis and those in various leguminous plants have been exploited in traditional rice prodnction systems to sustain yields of 2 to 4 t ha of grain withont fertilizer for hnndreds of years. 

Messi P, Guerrieri E, Bondi M (2005) Antibiotic resistance and antibacterial activity in heterotrophic bacteria of mineral water origin. Sci Total Environ 346(1-3) 213-219... 

Barbeau K, Rue EL, Trick CG, Bruland KW, Butler A (2003) Photochemical Reactivity of Siderophores Produced by Marine Heterotrophic Bacteria and Cyanobacteria Based on Characteristic Fe(III) Binding Groups. Lirrmol Oceanogr 48 1069... 

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