Bacteria mechanical issues

Finally, we consider acidification mechanisms specific to the continents so that ocean acidification is not an issue. Both enhanced respiration by surviving plant roots and bacterial decomposition of dead biomass witliin soils following Uie impact may have increased soil carbonic acid concentrations and soil weathering. (Dead biomass is also a source of alkalinity as Ca and other cations are released into the soil solution, but this process neutralized only a fraction of Uie total carbonic acid produced.) The subsurface soil biomass presently contains 2 x 10 moles C, which, if multiplied by -4 in the late Cretaceous, may liave been able to supply just enough carbonic acid to explain the foram Sr data. However, nearly all of the subsurface soil biomass would liave to have been decomposed by bacteria. Furthermore, the vast majority of CO2 released in soils diffuses out of the soil and joins the atmosphere [27], The numbers for plant root respiration are even less favorable. Presently, respiration accounts for 0.5 X 10 mol C yr released in soils. In the post-K/T impact atmosphere photosyntliesis was very likely interrupted for at least several months by dust and aerosols [7,8], so surviving plants would have had to respire at four times present biomass. One year of respiration yielded 2 x 10 mol CO2, not enough to weather Sr even if the CO2 remained in the soil. 

It has been suggested that bacteria may play a role in the transport of hydrophobic compounds in soils (Lindqvist and Enfield 1992), and it has been shown in batch experiments with Bacillus subtilis that sorption of 2,4,6-trichlorophenol may involve both neutral and anionic species (Daughney and Fein 1998). This mechanism could potentially apply also to aquatic systems where such processes could reasonably be included under particulate transport. There are, however, obvious unresolved issues concerning the subsequent desorption and bioavailability of these sorbed compounds. 

This book reviews some of the best-characterized chemotaxis systems, from bacteria to human eells. In so doing, the book demonstrates how basic chemotaxis is to life, how widespread it is, and how versatile its physiologieal funetions are. The book attempts to present the state of the art of a number of representative molecular mechanisms of chemotaxis, to indicate unanswered questions surrounding each mechanism, and to suggest future direetions for researeh. In some systems, the implications for health eonditions are diseussed. Thus, in the next chapter (Chapter 2), Joseph Lengeler surveys the systems and ph enomena in which chemotaxis appears to have a role. Some issues... 

It is now well identified that bacteria connect to solid supports to shape structured communities called biofilms, also known as biopolymer matrix-enclosed microbial populations adhering to each other and/or surfaces [111]. Biofihns occur on both living and inert supports in all environments [112]. They influence various industrial and domestic areas [113] and are accountable for a broad range of human diseases [111], In view of the ever growing number of implanted patients, biofilm-linked infections of indwelling medical devices are more predominantly a foremost public health issue. Various examples of implants that can be inflated by biofilm formation are mechanical heart valves, catheters, pacemakers/defibriUators, ventricular assist devices, vascular prostheses, coronary stents, neurosurgical ventricular shunts, cerebrospinal fluid shunts, neurological stimulation implants, ocular prostheses, inflatable penile, cochlear, joint prostheses, fracture-fixation devices, breast, and dental implants and contact lenses, intrauterine contraceptive devices [114-116]. 

Furthermore, just as photochemistry is a clean way to cause a reaction, it may offer a clean way to cause a movement in a macroscopic object. As a matter of fact, this is an issue rarely adopted by natme, where direct conversion of light into mechanical energy is limited to a few cases in bacteria [16]. This does not preclude adopting this principle for artificial system. As an example, one may think of controlling and directing the Brownian motion of molecules in solution and to induce directional translational and rotary motion of molecules or of nano-objects. In other words, rotary and translational motors may be devised and used to power future nanodevices. For example, rotary molecular motors allow the transmission of motion in multicomponent systems as well as reaching out-of-equilibrium assemblies (see Fig. 11.5) [18]. 

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