Prokaryotes properties

Assessment of novel prokaryotic properties through gene expresion... 

FIGURE 11.24 The properties of mRNA molecules in prokaryotic versus eukaryotic cells during transcription and translation. 

Moreno-Vivian C, P Cabello, M Martmez-Luque, R Blasco, F Castillo (1999) Prokaryotic nitrate reduction molecular properties and functional distinction among bacterial nitrate reductases. J Bacteriol 181 6573-6584. 

The occurrence in some plants of secondary metabolites characterized by an 0-heterocyclic structure and exhibiting antimicrobial properties is a well-known phenomenon [2,8-10]. Among them, catechins and proanthocyanidins are two classes of compounds exhibiting antimicrobial properties towards both prokaryotic and eukaryotic microorganisms. Yet, despite the large number of studies published so far, the real potentialities and limitations given by the use of this class of molecules as antiviral or antimicrobial (antibacterial, antimycotic, antiprotozoal) agents have not been critically evaluated. The present chapter represents an overview of the re-... 

The hypothesis that polar carotenoids regulate membrane fluidity of prokaryotes (performing a function similar to cholesterol in eukaryotes) was postulated by Rohmer et al. (1979). Thus, the effects of polar carotenoids on membrane properties should be similar in many ways to the effects caused by cholesterol. These similarities were demonstrated using different EPR spin-labeling approaches in which the effects of dipolar, terminally dihydroxylated carotenoids such as lutein,... 

Poly(3-hydroxybutyrate), poly(3HB), or PHB is a bacterially produced polyester which appears in bacterial cells as discrete granules. The capability of synthesizing poly(3HB) is widespread in prokaryotes [1-3]. This capability is neither a taxon-related property nor an ecophysiological peculiarity. It is largely inde-... 

An important point to note here and elsewhere in the description of cell activity is that the particular nature of calcium biochemistry, including the availability of the element and its necessary rejection from the prokaryote cell, when linked to stimulated input and interaction with specific internal proteins of selected properties, made it uniquely suitable for the function as an elementary ionic fast in/out messenger. It was then capable of signalling to cell changes once cell size and organisation increased beyond the elementary level of a cell with one small, rapidly... 

Lipid A constitutes the covalently bound lipid component and the least variable component of LPS (25). It anchors LPS to the bacterial cell by hydrophobic and electrostatic forces and mediates or contributes to many of the functions and activities that LPS exerts in prokaryotic and eukaryotic organisms. In the following sections, the primary structure of lipid A of different Gram-negative bacteria is described, together with some of its characteristic biological properties. Furthermore, this article describes some of the principal methods that have been used for the structural analysis of lipid A and discusses their merits and limitations. 

AsnRS was first characterized in the early 1960s in L. arabimsus hy its distinct chromatographic properties from aspartyl-tRNA synthetase and Asn synthetase and, at the end of the decade in E. coli as a protein of 90-100 kDa able to aminoacylate tRNA but not tRNA f / ° The enzyme was further characterized in mitochondria from Neurospora crassa" and in rat liver where tRNA asparaginylation activity was found associated with proteins of Air 35 and 90 kDa. The AsnRS purified from B. stearothermophilus of 127 kDa was characterized as a homodimer az (a = 51 kDa).AsnRSs isolated until now from various prokaryotic and eukaryotic organisms show conservation of the homodimeric structure. Investigation of B. stearothermophilus AsnRS allowed the determination of its physicochemical parameters S2o a = 6.6 x 10 s. 

Modern approaches based on the use of molecular techniques presumed to circumvent the need for culturing prokaryotes, fail to provide sufficient and reliable information for estimation of prokaryote diversity. Many properties that make these organisms important members of the living world are amenable to observation only through the study of living cultures. Since current culture techniques do not always satisfy the need of providing a balanced picture of the microflora composition, future developments in the study of bacterial diversity should include improvements in the culture methods to approach as closely as possible the conditions of natural habitats. Molecular methods of microflora analysis have an important role as guides for the isolation of new prokaryotic taxa. 

Although all tetracyclines have a similar mechanism of action, they have different chemical structures and are produced by different species of Streptomyces. In addition, structural analogues of these compounds have been synthesized to improve pharmacokinetic properties and antimicrobial activity. While several biological processes in the bacterial cells are modified by the tetracyclines, their primary mode of action is inhibition of protein synthesis. Tetracyclines bind to the SOS ribosome and thereby prevent the binding of aminoacyl transfer RNA (tRNA) to the A site (acceptor site) on the 50S ri-bosomal unit. The tetracyclines affect both eukaryotic and prokaryotic cells but are selectively toxic for bacteria, because they readily penetrate microbial membranes and accumulate in the cytoplasm through an energy-dependent tetracycline transport system that is absent from mammalian cells. 

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