Bacterial mobility

The principle goal of electrobioremediation is therefore to make bioaccessible compound, nutrient, and TEA fractions bioavailable and consequently increase biotransformation rates (Fig. 18.3). The following chapter will specify the impact of DC fields on bacterial mobilization in and deposition to subsurface matrices (Fig. 18.1b). 

The subsequent fate of the assimilated carbon depends on which biomass constituent the atom enters. Leaves, twigs, and the like enter litterfall, and decompose and recycle the carbon to the atmosphere within a few years, whereas carbon in stemwood has a turnover time counted in decades. In a steady-state ecosystem the net primary production is balanced by the total heterotrophic respiration plus other outputs. Non-respiratory outputs to be considered are fires and transport of organic material to the oceans. Fires mobilize about 5 Pg C/yr (Baes et ai, 1976 Crutzen and Andreae, 1990), most of which is converted to CO2. Since bacterial het-erotrophs are unable to oxidize elemental carbon, the production rate of pyroligneous graphite, a product of incomplete combustion (like forest fires), is an interesting quantity to assess. The inability of the biota to degrade elemental carbon puts carbon into a reservoir that is effectively isolated from the atmosphere and oceans. Seiler and Crutzen (1980) estimate the production rate of graphite to be 1 Pg C/yr. 

There are several environmentally significant mercury species. In the lithosphere, mercury is present primarily in the +II oxidation state as the very insoluble mineral cirmabar (HgS), as a minor constituent in other sulfide ores, bound to the surfaces of other minerals such as oxides, or bound to organic matter. In soil, biological reduction apparently is primarily responsible for the formation of mercury metal, which can then be volatilized. Metallic mercury is also thought to be the primary form emitted in high-temperature industrial processes. The insolubility of cinnabar probably limits the direct mobilization of mercury where this mineral occurs, but oxidation of the sulfide in oxygenated water can allow mercury to become available and participate in other reactions, including bacterial transformations. 

The evolutionary history of symbiotic nitrogen fixers is therefore a tale of coevolution, which occurred in the shadow of their hosts, chasing their growing roots, and striving for adaptation. It is an example of how bacterial genetics has managed to keep pace with the creative power of eukaryotic sexual recombination. Mobile replicons, insertion elements, and symbiotic islands prone to move have helped rhizobia to succeed in their pursuit. The race, naturally, is not over and, looking at it from a distance, what we have. seen, compared to what we have yet to see, is probably just a cloud of dust. 

Many examples of mobile elements are found in bacteria, where they are called transpo-sons. Bacterial transposons have terminal repeat sequences that both code for the enzymes catalyzing the process of transposition (transposases) and physically interact with these enzymes to bring them to the DNA target site. At this site the DNA-bound transposase presumably catalyzes the endonucleolytic cleavage of the terminal repeat sequence of the trahsposon and also catalyzes a similar sequence in the target DNA. 

Historically, respirometers have been used for wastewater biodegradability evaluation. More recently [52], a mobile on-line respirometer was proposed and tested for monitoring the activated sludge inhibition due to industrial discharges in a sewer network. A derived portable device called a Baroxymeter [53], based on monitoring the respiration of a bacterial culture by pressure measurements and using respiration inhibition as a toxicity alert, was proposed for the rapid detection of the toxicity effect of some toxic substances. 

R.T. Vinopal, J.R. Jadamec, P. deFur, A.L. Demars, S. Jakubielski, C. Green, C.P. Anderson and J.E.D.R.F. Dugas, Fingerprinting bacterial strains using ion mobility spectrometry, Anal. Chim. Acta, 457 (2005) 83-95. 

About a quarter of the total body iron is stored in macrophages and hepatocytes as a reserve, which can be readily mobilized for red blood cell formation (erythropoiesis). This storage iron is mostly in the form of ferritin, like bacterioferritin a 24-subunit protein in the form of a spherical protein shell enclosing a cavity within which up to 4500 atoms of iron can be stored, essentially as the mineral ferrihydrite. Despite the water insolubility of ferrihydrite, it is kept in a solution within the protein shell, such that one can easily prepare mammalian ferritin solutions that contain 1 M ferric iron (i.e. 56 mg/ml). Mammalian ferritins, unlike most bacterial and plant ferritins, have the particularity that they are heteropolymers, made up of two subunit types, H and L. Whereas H-subunits have a ferroxidase activity, catalysing the oxidation of two Fe2+ atoms to Fe3+, L-subunits appear to be involved in the nucleation of the mineral iron core once this has formed an initial critical mass, further iron oxidation and deposition in the biomineral takes place on the surface of the ferrihydrite crystallite itself (see a further discussion in Chapter 19). 

Relation between bacterial adhesion to sulphated polystyrene (A) and cell surface characteristics as determined by electrophoretic mobility and contact angle measurement. Results were obtained by interpolating the data points for the adhesion of 17 different strains of bacteria. 

Do not use aqueous buffered mobile phase older than 10 days because of the increased risk of bacterial growth, which can damage the HPLC column. ... 

Simon R. 1984. High frequency mobilization of Gram-negative bacterial replicons by the in vitro constructed Tn5-Mob transposon. Mol Gen Genet 196 413-20. 

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