Microorganisms, penetration membranes

Based upon these resnlts, it is highly probable that waterborne lipophilic chemicals contiibnte to the observed deformities in amphibian popnlations at the impacted site. It is highly improbable that microorganisms or virnses originating from the lake water conld have cansed the deformities becanse the transport corridors in the SPMD membrane are no more than 10 A in cross-sectional diameter (far too small to allow virnses to penetrate the sampler membrane). 

However the mechanism of the antimicrobial effect of silver nanoparticles is not well understood. It has been recently reported that Nanosilver represents a special physicochemical system which confers its antimicrobial activities via Ag-t [11]. According to Morones et al., the bactericidal effect of silver nanoparticles on microorganisms is connected not merely with the release of silver ions in solution [12]. Silver nanoparticles can also be attached to the surface of the cell membrane and drastically distnrb its proper function [12]. They could also penetrate inside the bacteria and canse farther damage by interacting with sulfur and phosphorus-containing componnds snch as DNA. 

Ionophores are substances that can penetrate a membrane and increase its permeability to ions. They transport ions in both directions across a membrane. Consequently, they will only reduce the concentration of a specific ion until its concentration is the same on both sides of a membrane. This reduction in the concentration of essential cell components of a microorganism is often sufficient to lead to the distruction of the organism. 

Hydroxyl radicals are probably the most toxic for microorganisms [30], They promote peroxidation of polyunsaturated phospholipid components of the lipid membrane and induce disorder in the cell membrane [31]. The damage of the outer membrane increases the permeability to ROSs. This process is possible thanks to a sufficient lifetime of ROSs generated at the Ti02 surface. ROS diffusion was studied by Fujishima et al. Their experiments demonstrated the bactericidal effect of irradiated Ti02 film on E. coli even at the distance of 50pm from the film [21], Furthermore, oxidative perforation of the cellular membrane allows the photocatalyst nanoparticles to penetrate the interior of the cell, causing severe, efficient oxidation of the cell content [27,32], ROSs are responsible for oxidation of amino acids, peptides [33], enzymes [34], and nucleic acids [32, 35-37]. Destruction of... 

There has been much discussion in the literature as to whether or not microorganisms can penetrate a membrane of pore structure smaller than the organism. Experience in filtration through porous media em-... 

It was during the preparation of this type of dialysate that membrane penetration by microorganisms became the subject of debate. We wanted... 

Park, C. B., Kim, H. S. and Kim, S. C. (1998) Mechanism of action of the antimicrobial peptide buforin II Buforin II kills microorganisms by penetrating the cell membrane and inhibiting cellular functions. Biochemical and Biophysical Research Communications, 244(1), 253-257. 

Some organic acids have no inhibitory effect on microorganisms for example, gluconic acid is a highly polar molecule, and is unable to penetrate the cell membrane of E. coli 0157 H7 (Bjornsdottir, Breidt, Jr., and McFeeters, 2006). A tolerance response in Salmonella enterica sv. Typhimurium, induced by lactic acid, will, however, induce sensitivity to hydrogen peroxide (Greenacre et al., 2006). 

In the presence of diluent molecules in the extracellular medium, microorganisms tend to decrease the fluidity of their cytoplasmic membranes. The decreased fluidity of the cytoplasmic membrane increases its rigidity and viscosity, thus reducing the ability of the diluent molecules to penetrate into the structure of the cytoplasmic membrane [2]. Three mechanisms by which the fluidity of the cytoplasmic membrane can be decreased have been reported in the literature to date. The first one is the homeoviscous adaptation which involves changing the proportions of fatty acids in the membrane hpids [19, 22-25]. The second mechanism is the increase in the relative concentration of proteins relative to hpids in the cytoplasmic membrane [26]. The third mechanism involves the change in ceU shape and has been reported for archae [18]. 

N,N-Dimethyldithiocarbamates do not form isothiocyanates, so their mode of action as fungicides is different from that of the afore-mentioned substances. TMTD penetrates the cell membrane of fungi more easily than dimethyldithio-carbamates, and is then reduced within the cell (Richardson and Thorn, 1961) so that its action is the same as that of dimethyldithiocarbamates. However, the fact that TMTD is more toxic to several microorganisms than the sodium salt of dimethyidithiocarbamic acid indicates that there must be a certain nonessential difference between the two active substances. Owens and Rubinstein (1964) proved in vitro the different reactivity of TMTD and of the other dimethyldithiocarbamates towards 4-nitrothiophenol. However, in the primary reaction of TMTD dimethyl-... 

If it is to be considered that microorganisms can penetrate capillaries with diameters as small as 0.4 pm (and this is a reasonable assumption, because Pseudomonas diminuta was first icountered from having passed through filter membranes with 0.45 pm pone size ratings), Poiseuille s law can be used to calculate the dimensions of a satisfactory vacuum dye penetration test. 

In a porous body, the surface area available to a reactant will depend upon the relative sizes of the pores and the penetrating substance. Thus, in the case of wood and its attack by microorganisms, the latter are so large in comparison to pit membrane pores that the initial attack must... 

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