Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “microbial evolution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed2006

The future of infection imaging.

Over the past 10 years, there has been an unprecedented explosion in new agents suggested for imaging infection. These agents have been based on our understanding of the processes involved in invasive infection of the body by microorganisms and the body's response to them. Work with antibodies has traditionally yielded the most likely candidates, 3 of which have entered clinical use in Europe and the USA. However, the expense and limitations of producing antibodies have resulted in investigations into the use of cytokine and anti-microbial radiolabelled peptides. This work is very promising in that these types of tracers may be more specific for infection than labelled leukocytes. There remains a big question mark, however, as to whether or not these will progress from phase I/II trials to phase III trials and, ultimately, to clinical use. Finally, the investigation of radiolabelled anti-microbials continues and may prove to be most useful with anti-fungals especially in the immuno-suppressed host. We live in exciting times in the evolution of infection imaging; time and commercial constraints will determine which, if any of these tracers make it to the market and will they do so before PET rules all nuclear medicine?

Antibodies, Monoclonal↗
PubMedDate not supplied

[Microbial inhibitors of lysozyme].

Lysozyme is one of the most important factors of innate immunity, possessing anti-microbial action against a wide range of microorganisms due to cationic nature of protein and, in a lesser degree, due to muramidase activity. In the process of evolution, different mechanisms of lysozyme inhibition, defined as anti-lysozyme activity (ALA), were formed in microorganisms. The usage of the delayed antagonism principle allowed to reveal anti-lysozyme sign in microorganisms of different phylogenetic groups. In the review, data on the occurrence and level of anti-lysozyme activity in pathogens and representatives of normal microflora were presented; findings on nature and genetic determinants of lysozyme inhibitors are given. questions on drug regulation of ALA of the causative agents in infectious diseases and dysbiotic conditions are discussed.

Animals↗
PubMed1984

The structure and expression of the mercury-resistance transposon Tn501.

The nucleotide sequence of the mercury-resistance transposon Tn501 has been determined and the functional regions have been identified by a variety of techniques. The transposition gene products are structurally and functionally homologous to those of other transposons in the Tn3 family and of other recombination systems. The expression of the transposition genes may be regulated coordinately with that of the mercury-resistance genes. Comparison of related transposons suggests mechanisms for their evolution.

Base Sequence↗
PubMed2025

Orthogonal replication with optogenetic selection evolves yeast JEN1 into a mevalonate transporter.

The in vivo continuous evolution system OrthoRep (orthogonal replication) is a powerful strategy for rapid enzyme evolution in Saccharomyces cerevisiae that diversifies genes at a rate exceeding the endogenous genome mutagenesis rate by several orders of magnitude. However, it is difficult to neofunctionalize genes using OrthoRep partly because of the way selection pressures are applied. Here we combine OrthoRep with optogenetics in a selection strategy we call OptoRep, which allows fine-tuning of selection pressure with light. With this capability, we evolved a truncated form of the endogenous monocarboxylate transporter JEN1 (JEN1t) into a de novo mevalonate importer. We demonstrate the functionality of the evolved JEN1t (JEN1tY180C/G) in the production of farnesene, a renewable aviation biofuel, from mevalonate fed to fermentation media or produced by microbial consortia. This study shows that the light-induced complementation of OptoRep may improve the ability to evolve functions not currently accessible for selection, while its fine tunability of selection pressure may allow the continuous evolution of genes whose desired function has a restrictive range between providing effective selection and cellular viability.

Saccharomyces cerevisiae↗
PubMed2005

Dynamics of indigenous yeast populations during spontaneous fermentation of wines from Mendoza, Argentina.

Fermentation of wine is a complex microbial reaction, which involves the sequential development of various species of yeasts and lactic acid bacteria. Of these, yeasts are the main group responsible for alcoholic fermentation. The aim of this work was to study, under industrial conditions, the evolution of yeast populations and to describe the individual evolution of the most important yeasts during three spontaneous fermentations of Malbec musts from Argentina. This work shows the significant participation of non-Saccharomyces yeasts during spontaneous fermentation of musts, with the ubiquitous presence of three main species: Kloeckera apiculata, Candida stellata and Metschnikowia pulcherrima.

Colony Count, Microbial↗
PubMed1979

Toxicity of NO(2): Effect of Nitrite on Microbial Activity in an Acid Soil.

In an acid forest soil of pH 4.0 to 4.2 amended with glucose, 1.0 mug of nitrite-N per g of soil inhibited the rate of O(2) utilization and CO(2) evolution. The inhibition was evident only for several hours after nitrite addition, and the subsequent rate of glucose mineralization was the same as in soil not receiving nitrite. The decomposition of protein hydrolysate was reduced by 10 mug of nitrite-N per g of soil but not lower concentrations, and the inhibition of this process by 20 mug of nitrite-N per g had dissipated after 24 h. Nitrite disappeared readily from this soil. More than 20 mug of bisulfite-S per g of soil was required to inhibit glucose decomposition. The data suggest that the possible antimicrobial effects of low levels of NO(2), which give rise to nitrite in soil, require further evaluation.

Journal Article↗
PubMed1987

Enzymes and genes of microbial autotrophy.

Ribulose 1,5-bisphosphate carboxylase/oxygenase and phosphoribulokinase are enzymes which are unique to, and essential for, the operation of the Calvin cycle. Biochemical and genetic studies of these enzymes in autotrophic bacteria are providing information on the evolution of autotrophy, regulation of CO2 assimilation and on the prospects of increasing plant productivity.

Bacteria↗
PubMed2006

The evolution of putative starch-binding domains.

The present bioinformatics analysis was focused on the starch-binding domains (SBDs) and SBD-like motifs sequentially related to carbohydrate-binding module (CBM) families CBM20 and CBM21. Originally, these SBDs were known from microbial amylases only. At present homologous starch- and glycogen-binding domains (or putative SBD sequences) have been recognised in various plant and animal proteins. The sequence comparison clearly showed that the SBD-like sequences in genethonin-1, starch synthase III and glucan branching enzyme should possess the real SBD function since the two tryptophans (or at least two aromatics) of the typical starch-binding site 1 are conserved in their sequences. The same should apply also for the sequences corresponding with the so-called KIS-domain of plant AKINbetagamma protein that is a homologue of the animal AMP-activated protein kinase (AMPK). The evolutionary tree classified the compared SBDs into three distinct groups: (i) the family CBM20 (the motifs from genethonins, laforins, starch excess 4 protein, beta-subunits of the animal AMPK and all plant and yeast homologues, and eventually from amylopullulanases); (ii) the family CBM21 (the motifs from regulatory subunits of protein phosphatase 1 together with those from starch synthase III); and (iii) the (CBM20+CBM21)-related group (the motifs from the pullulanase subfamily consisting of pullulanase, branching enzyme, isoamylase and maltooligosyl trehalohydrolase).

Animals↗
PubMedDate not supplied

[A microbial growth study in parenteral nutrition].

Study on the behaviour of five microorganisms in different formulations of parenteral nutrition (PN) different from each other with regard to the presence or absence of lipids and the addition of vitamins or oligoelements. The bacteria investigated were Staphylococcus aureus (ATCC 12600), Bacillus subtilis (ATCC 6051), Pseudomonas aeruginosa (ATCC 9027) and Enterobacter cloacae (ATCC 13047), as well as Candida albicans (LSH 3156 D). It was observed that C. albicans grew well in all types of PN tested, S. aureus and E. cloacae showed growth in the formulations containing lipids, whereas in those lacking lipids, the number of microorganisms remained practically uniform. P. aeruginosa remained essentially constant throughout the study and in all mixtures and B. subtilis was reduced with regard to the number of feasible organisms, due to the formation of spores. Finally, the addition of vitamins or oligoelements did not appear to determine a particular model of evolution in any of the species studied.

Bacteria↗
PubMed2000

Bacteriophytochromes: new tools for understanding phytochrome signal transduction.

The recent discovery of phytochrome-like photoreceptors, collectively called bacteriophytochromes, in a number of bacteria has greatly expanded our understanding of the origins and modes of action of phytochromes in higher plants. These primitive receptors contain an N-terminal domain homologous to the chromophore-binding pocket of phytochromes, and like phytochromes, they bind a variety of bilins to generate photochromic holoproteins. Following the chromophore pocket is a domain similar to two-component histidine kinases, suggesting that these bacterial photoreceptors function in phosphorelay cascades that respond to the light environment. Their organization and distribution support the views that higher-plant phytochromes evolved from a cyanobacterial precursor and that they act as light-regulated kinases. With the ability to exploit bacterial genetics, these bacteriophytochromes now offer simple models to help unravel the biochemical and biophysical events that initiate phytochrome signal transmission.

Amino Acid Sequence↗
PubMed2004

Identification and sequence analysis of chicken Toll-like receptors.

Toll-like receptors (TLRs) play an important role in the recognition of microbial components. Only chicken TLR2 and -4 have been reported in the literature. The objectives of this study were to identify new chicken TLRs and to evaluate evolutionary significance of these receptors. Searching chicken genomic databases and DNA sequencing revealed five new TLRs, TLR1 (type 1 and 2), -3, -5, and -7. No chicken orthologues of mammalian TLR8, -9, or -10 were found. As in mammals, all chicken TLRs (chTLRs) share identical protein secondary structure that consists of several leucine-rich domains, a transmembrane domain, and Toll/Interleukin-1 receptor domain(s). Phylogenetic analyses indicate that the identified chTLR genes are the orthologues of TLRs in mammals. Analyses of the number of synonymous substitutions per synonymous site and nonsynonymous substitutions per nonsynonymous site indicate that the nucleotide sequences coding for the leucine-rich repeats of chicken TLR1 type 1 and type 2 were significantly under positive Darwinian selection. In contrast, the sequences of other TLRs were under purifying selection. These results support the hypothesis that one of the major evolutionary strategies of the innate immune system is to recognize a few highly conserved microbial components with several conserved TLRs. The results also indicate that the sequence changes in the ligand-binding domains of TLR1 in chickens provide adaptive advantages during evolution.

Amino Acid Sequence↗
PubMed2006

The compatibility of a nucleopolyhedrosis virus control with resistance management for Bacillus thuringiensis: co-infection and cross-resistance studies with the diamondback moth, Plutella xylostella.

The use of genetically modified crops expressing Bacillus thuringiensis (Bt) toxins can lead to the reduction in application of broad-spectrum pesticides and an increased opportunity for supplementary biological control. Bt microbial sprays are also used by organic growers or as part of integrated pest management programs that rely on the use of natural enemies. In both applications the evolution of resistance to Bt toxins is a potential problem. Natural enemies (pathogens or insects) acting in combination with toxins can accelerate or decelerate the evolution of resistance to Bt. In the present study we investigated whether the use of a nucleopolyhedrovirus (AcMNPV) could potentially affect the evolution of resistance to the Bt toxin Cry1Ac in Plutella xylostella. At low toxin doses there was evidence for antagonistic interactions between AcMNPV and Cry1Ac resistant and susceptible insects. However, this antagonism was much stronger and more widespread for susceptible larvae; interactions were generally not distinguishable from additive for resistant larvae. Selection for resistance to Cry1Ac in two populations of P. xylostella with differing resistance mechanisms did not produce any correlated changes in resistance to AcMNPV. Stronger antagonistic interactions between Bt and AcMNPV on susceptible rather than resistant larvae can decrease the relative fitness between Bt-resistant and susceptible larvae. These interactions and the lack of cross-resistance between virus and toxin suggest that the use of NPV is compatible with resistance management to Bt products.

Animals↗
PubMed1987

Nucleotide sequence and organization of the human S-protein gene: repeating peptide motifs in the "pexin" family and a model for their evolution.

The S-protein/vitronectin gene was isolated from a human genomic DNA library, and its sequence of about 5.3 kilobases including the adjacent 5' and 3' flanking regions was established. Alignment of the genomic DNA nucleotide sequence and the cDNA sequence indicated that the gene consisted of eight exons and seven introns. The intron positions in the S-protein gene and their phase type were compared to those in the hemopexin gene which shares amino acid sequence homologies with transin and the S-protein. Three introns have been found at equivalent positions; two other introns are very close to these positions and are interpreted as cases of intron sliding. Introns 3-7 occur at a conserved glycine residue within repeating peptide segments, whereas introns 1 and 2 are at the boundaries of the Somatomedin B domain of S-protein. The analysis of the exon structure in relation to repeating peptide motifs within the S-protein strongly suggests that it contains only seven repeats, one less than the hemopexin molecule. A very similar repeat pattern like that in hemopexin is shown to be present also in two other related proteins, transin and interstitial collagenase. An evolutionary model for the generation of the repeat pattern in the S-protein and the other members of this novel "pexin" gene family is proposed, and the sequence modifications for some of the repeats during divergent evolution are discussed in relation to known unique functional properties of hemopexin and S-protein.

Amino Acid Sequence↗
PubMed2001

A metabolic node in action: chorismate-utilizing enzymes in microorganisms.

The shikimate pathway has been described as a metabolic tree with many branches that led to the synthesis of an extensive range of products. This pathway is present only in bacteria, fungi, and plants. While there is only little difference in the sequence of the chemical reactions of the pathway, significant differences exist in terms of organization and regulation. In the main trunk of the shikimate pathway, D-erythrose 4-phosphate and phosphoenolpyruvate are converted via shikimate to chorismate. Chorismate is the common precursor for the biosynthesis of the aromatic amino acids, phenylalanine, tyrosine, and tryptophan, but also for other products as diverse as folate cofactors, benzoid and naphthoid coenzymes, phenazines, and siderophores. Five chorismate-utilizing enzymes have been characterized in microorganisms: chorismate mutase, anthranilate synthase, aminodeoxychorismate synthase, isochorismate synthase, and chorismate pyruvate-lyase. In this review these enzymes are discussed in terms of the corresponding gene structures and regulation, nucleotide and protein sequences, protein structures, and reaction mechanisms. The main emphasis is on transcriptional and posttranslational regulatory mechanisms, in view of how a microbial cell exploits its chorismate pool in diverse anabolic pathways. Comparison of the chorismate-utilizing enzymes has shown that some of them share sequence similarity, suggesting divergent evolution and commonality in reaction mechanisms. However, other chorismate-utilizing enzymes are examples of convergent evolution toward similar reaction capabilities.

Anthranilate Synthase↗
PubMed2003

Analysis of genomic diversity and evolution of the low-level antiseptic resistance gene smr in Staphylococcus aureus.

A multidrug efflux pump specified by the smr gene mediates low-level antiseptic resistance in staphylococci. We analyzed the genomic diversity of smr and its gene cassette, a structural unit containing smr and terminal direct repeats (DRs), in 22 clinical strains of Staphylococcus aureus isolated over 9 years in a Japanese hospital. Although open reading frames (ORFs) of all the smr genes examined were identical to those reported previously (e.g., qacD in pSK41), smr gene cassettes were classified into three groups (types 1, 2, and 3). The type 1 cassette had an identical genetic organization to that found in the plasmid pSK41, a putative prototype of the smr gene cassette, which contains DRs flanking smr. In the type 2 cassette, the rep gene and a putative replication nick site were found upstream of smr, between a SSOA (single-strand origin) sequence and DR1c, which are components of the type 1 cassette DR. In the type 3 cassette detected in a single strain, IS431 was located between the 3' end of smr and DR. It was suggested by genomic comparison that type 2 and type 3 cassettes might have been derived from the type 1 cassette via insertion of foreign DNA sequence, and that the type 2 cassette might be a precursor form of some previously reported smr cassettes, such as those in pSK108 and pNVH99. Although MICs of antiseptics and ethidium bromide were generally the same among strains having type 1, 2, or 3 smr gene cassette, the type 1 cassette was detected most frequently. Moreover, the copy number of the smr gene in the type 2 cassette was found to be much higher than that in the type 1 or type 3 cassette.

Anti-Bacterial Agents↗