Bacterial species

Certain bacterial species produce polymers of y-hydroxybutyric acid and other hydroxyalkanoic acids as storage polymers. These are biodegradable polymers with some desirable properties for manufacture of biodegradable packaging materials, and considerable effort is being devoted by ICI Ltd. and others to the development of bacterial fermentation processes to produce these polymers at a high molecular weight (66). 

Resistance to Tetracyclines. The tetracyclines stiU provide inexpensive and effective treatment for several microbial infections, but the emergence of acquired resistance to this class of antibiotic has limited their clinical usehilness. Studies to define the molecular basis of resistance are underway so that derivatives having improved antibacterial spectra and less susceptibiUty to bacterial resistance may be developed. Tetracyclines are antibiotics of choice for relatively few human infections encountered in daily clinical practice (104), largely as a result of the emergence of acquired tetracycline-resistance among clinically important bacteria (88,105,106). Acquired resistance occurs when resistant strains emerge from previously sensitive bacterial populations by acquisition of resistance genes which usually reside in plasmids and/or transposons (88,106,107). Furthermore, resistance deterrninants contained in transposons spread to, and become estabUshed in, diverse bacterial species (106). 

It was established that Ab to Klebsiella pneumoniae didn t demonstrate the cross-reactivity to antigens of the relative bacterial species so, it could be considered that antibodies investigated was highly specific only to the own antigen. The physical-chemical characteristics of the immunological interaction such as constants of formation of Ag-Ab complex were obtained. The binding constants of immune complex were Ka =(9.7 l.l)-10 and Ka,=(1.7+0.3)T0 (mg/ml)f... 

Comparison of the amino acid sequences of the L and M subunits of the reaction centers from three different bacterial species shows that about 50% of all residues in those two subunits are conserved in all three species. In the transmembrane helices, sequence conservation varies. Residues that are buried and have contacts either with pigments or with other transmembrane helices are about 60% conserved. In contrast, residues that are fully exposed to the membrane lipids are only 16% conserved. Clearly, fewer restrictions... 

P. phosphoreum. In the case of A. fischeri, the total amount of aldehydes was only 15% of that from P. phosphoreum, which consisted of dodecanal (36%), tetradecanal (32%) and hexadecanal (20%). The contents of aldehydes having the carbon atoms of 10, 11, 13, 15, 17 and 18 were negligibly small in both bacterial species. 

Another notable feature of the in vivo bacterial luminescence is seen in their emission spectra. Although the emission peak of in vitro bacterial luminescence is normally at about 490 nm, the in vivo emission peaks of various bacterial species and strains are significantly shifted from 490 nm, ranging from the shortest wavelength of 472 nm to over 500 nm. Some expanded notes concerning in vivo bacterial luminescence are given below. 

Energy transfer to fluorescent proteins. There are marked differences among the various bacterial species and strains in terms of the in vivo luminescence spectra. The emission maxima are spread mostly in a range from 472 to 505 nm (Seliger and Morton, 1968), but one of the strains, P. fischeri Y-l, shows a maximum at 545 nm (Ruby and Nealson, 1977), as shown in Fig. 2.3. However, the in vitro luminescence spectra measured with purified luciferases obtained from the various bacterial species and strains are all similar (Amax about 490 nm). The variation in the in vivo luminescence spectra may be due to the occurrence of an intermolecular energy transfer that increases the efficiency of light emission. 

Microbial Resistance to Drugs. Figure 1 MlC-distribution showing the number of isolates of one species with a certain MIC. Some bacterial species are naturally resistant (intrinsic resistance) to drugs because their natural MIC is above the breakpoint. Naturally sensitive isolates as well as naturally resistant ones can acquire resistance and with that increase their MIC (acquired or secondary resistance). 

Unquestionably, there are limitations to such a procedure, and because calculations for two specimens failed, they lead to an even higher deviation from the control signal. These limits have to be defined by future work. The model experiment is only an approach to collagen diagenesis in buried bone. In nature, more than one bacterial species feeds from bone protein, and a... 

It transpires that the heat shock genes of one single bacterial species are regulated by different mechanisms. Genes and operons controlled by one particular regulator are called regulons and, if there are at least two regulons in one species induced by the same stress factor, they form a stimulon. 

Structure and form of the bacterial cell 6 Properties of selected bacterial species... 

F-pili or sex strands are partofa primitive genetic exchange system in some bacterial species. Part of the genetic material may be passed from one cell to another through the hollow pilus, thus giving rise to a simple form of sexual reproduction. 

Some bacterial species accumulate material as a coating of varying degrees of looseness. If the material is reasonably discrete it is called a capsule, if loosely bound to the surface it is called slime. 

Some bacterial species produce pigments during their growth which give the colonies a characteristic colour. 

Most bacteria grow best at pH valnes of 7.4-7.6, on the alkaline side of neutrahty, but some bacterial species are able to grow at pH 1-2 or 9-9.5, although they are exceptional. 

The induction of a lysogenic culture to produce infectious phages, followed by lysogenization of a second strain of the bacterial species by these phages, results in the... 

Different strains of a number of bacterial species can be distinguished by their sensitivity to a collection of phages. Bacteria which can be typed in this way include Stop/ , aureus and Salmonella typhi. The particular strain ol say, Staph, aureus responsible for an outbreak of infection is characterized by the pattern of its sensitivity to a standard set of phages and then possible sources of infection are examined for the presence of that same phage type of Staph, aureus. 

Bacterial resistance to antibiotics has been recognized since the first drugs were introduced for clinical use. The sulphonamides were introduced in 1935 and approximately 10 years later 20% of clinical isolates of Neisseria gonorrhoeae had become resistant. Similar increases in sulphonamide resistance were found in streptococci, coliforms and other bacteria. Penicillin was first used in 1941, when less than 1 % of Staphylococcus aureus strains were resistant to its action. By 1947,3 8% of hospital strains had acquired resistance and currently over 90% of Staph, aureus isolates are resistant to penicillin. Increasing resistance to antibiotics is a consequence of selective pressure, but the actual incidence of resistance varies between different bacterial species. For example, ampicillin resistance inEscherichia coli, presumably under similar selective pressure as Staph, aureus with penicillin, has remained at a level of 30-40% for mai years with a slow rate of increase. Streptococcus pyogenes, another major pathogen, has remained susceptible to penicillin since its introduction, with no reports of resistance in the scientific literature. Equally, it is well recognized that certain bacteria are unaffected by specific antibiotics. In other words, these bacteria have always been antibiotic-resistant. 

Rifampicin is the semisynthetic derivative used widely in the UK. Resistance to rifampicin is primarily due to chromosomal mutations resulting in an altered RNA polymerase which is less well inhibited by the drug. The mutations tend to be clustered within short conserved regions of the J3 subunit gene of RNA polymerase. Similar mutations have been found in all bacterial species studied thus far. 

Guerin WF, SA Boyd (1992) Differential bioavailability of soil-sorbed naphthalene by two bacterial species. Appl Environ Microbiol 58 1142-1152. 

DeMoss RD, K Moser (1969) Tryptophananase in diverse bacterial species. J Bacteriol 98 167-171. 

Various bacterial species have proven useful in MEOR. The principle is based on the species biochemical byproducts produced, such as gases, surfactants, solvents, acids, swelling agents, and cosurfactants, which facilitate the displacement of oil. In field experiments, in situ fermentation is often desirable for producing a great quantity of gases. Clostridium hydrosulfuricum 39E was found to have surface-active properties during simulated enhanced oil recovery experiments [1874]. 

Any bacterial species living in a mixed microbial population, such as that of the rhizosphere, may encounter not only the molecular signal produced by a cell of the. same species but also molecular signals produced by cells of different species. The situation is made more complex by the presence of plant molecular signals, and by the fact that the same AHL molecule can be used to regulate the... 

Figure 1 N-acyl homoserine lactone nucleotides produced by some bacterial species and their phenotype function (From Refs. 34 and 35).

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