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Restriction and modification of typing phages by an R factor in S. typhi.

We have investigated the qualities of one R factor 552 discovered on a strain of S. typhi resistant to A, C, S, T, nontypable, isolated from stool cultures; from the same patient, before starting the treatment we isolated, from his blood sample, the strain S. typhi 221, sensitive to A, C, T, degraded phage-type Vi A. Factor R 552 fi- when infecting strains of S. typhi Vi A and of A degraded 221- leads to the conversion of the respective phage-types into non-typable ones, as a result of the restricting and modifying effect on phage Vi A and on the derivatives resulting from it. Derivative R 552-1 as a resistance marker to ampicilline has a restrictive effect on the phage of S. panama A 47 too. Not taking into account possible causes such as spontaneous mutation, lysogeny, and adsorption of phages, we reach for the conclusion that R factor 552, through is restrictive effect, is the only cause responsible for the existence in the same patient of two strains of S. typhi different from the point of view of phage-type and antibiotype.

Bacteriophage Typing↗

Health considerations regarding horizontal transfer of microbial transgenes present in genetically modified crops.

The potential effects of horizontal gene transfer on human health are an important item in the safety assessment of genetically modified organisms. Horizontal gene transfer from genetically modified crops to gut microflora most likely occurs with transgenes of microbial origin. The characteristics of microbial transgenes other than antibiotic-resistance genes in market-approved genetically modified crops are reviewed. These characteristics include the microbial source, natural function, function in genetically modified crops, natural prevalence, geographical distribution, similarity to other microbial genes, known horizontal transfer activity, selective conditions and environments for horizontally transferred genes, and potential contribution to pathogenicity and virulence in humans and animals. The assessment of this set of data for each of the microbial genes reviewed does not give rise to health concerns. We recommend including the above-mentioned items into the premarket safety assessment of genetically modified crops carrying transgenes other than those reviewed in the present study.

Journal Article↗

Complementation and genetic recombination in Candida lipolytica.

Nutritional requirements were introduced into wild-type, heterothallic strains of Candida lipolytica by exposing the cells to X rays. Complementing hybrids were recovered from mixtures of the auxotrophic strains, and genetic recombination was observed in individually isolated ascospores from the hybrid strains.

Canavanine↗

Microbial rhodopsins: functional versatility and genetic mobility.

The type 1 (microbial) rhodopsins are a diverse group of photochemically reactive proteins that span the three domains of life. Their broad phylogenetic distribution has motivated conjecture that rhodopsin-like functionality was present in the last common ancestor of all life. Here, we discuss the evolution of the type 1 microbial rhodopsins and document five cases of lateral gene transfer (LGT) between domains. We suggest that, thanks to the functional versatility of these retinylidene proteins and the relative ease with which they can complement the existing energy-generating or photosensory repertoires of many organisms, LGT is in fact the principal force that determines their broad but patchy distribution.

Evolution, Molecular↗

[Drug-resistance markers from Salmonellae in Pasteurella multocida].

A transfer of resistance was effected of S. haidelberge strain, having 7 medicinal resistance markers, onto 2 Pasteurella multocida strains No. 10 and Vladislavovo. In strain No. 10 were found 20% of recombinations, whereas in Vladislavovo their number was 10%, hence the different pasteurella strains can be recipients at a higher or lower degree. The recombinations obtained are not stable and during their short conservation in bouillon they spontaneously get rid of the markers of resistance acquired.

Drug Resistance, Microbial↗

Ab initio genotype-phenotype association reveals intrinsic modularity in genetic networks.

Microbial species express an astonishing diversity of phenotypic traits, behaviors, and metabolic capacities. However, our molecular understanding of these phenotypes is based almost entirely on studies in a handful of model organisms that together represent only a small fraction of this phenotypic diversity. Furthermore, many microbial species are not amenable to traditional laboratory analysis because of their exotic lifestyles and/or lack of suitable molecular genetic techniques. As an adjunct to experimental analysis, we have developed a computational information-theoretic framework that produces high-confidence gene-phenotype predictions using cross-species distributions of genes and phenotypes across 202 fully sequenced archaea and eubacteria. In addition to identifying the genetic basis of complex traits, our approach reveals the organization of these genes into generic preferentially co-inherited modules, many of which correspond directly to known enzymatic pathways, molecular complexes, signaling pathways, and molecular machines.

Bacteria↗