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Reduction of bacterial genome size and expansion resulting from obligate intracellular lifestyle and adaptation to soil habitat.

100%
Stępkowski T., Legocki A. B.
Acta Biochimica Polonica
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2001
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vol. 48
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issue 2
367-381
EN
Prokaryotic organisms are exposed in the course of evolution to various impacts, resulting often in drastic changes of their genome size. Depending on circumstances, the same lineage may diverge into species having substantially reduced genomes, or such whose genomes have undergone considerable enlargement. Genome reduction is a consequence of obligate intracellular lifestyle rendering numerous genes expendable. Another consequence of intracellular lifestyle is reduction of effective population size and limited possibility of gene acquirement via lateral transfer. This causes a state of relaxed selection resulting in accumulation of mildly deleterious mutations that can not be corrected by recombination with the wild type copy. Thus, gene loss is usually irreversible. Additionally, constant environment of the eukaryotic cell renders that some bacterial genes involved in DNA repair are expandable. The loss of these genes is a probable cause of mutational bias resulting in a high A+T content. While causes of genome reduction are rather indisputable, those resulting in genome expansion seem to be less obvious. Presumably, the genome enlargement is an indirect consequence of adaptation to changing environmental conditions and requires the acquisition and integration of numerous genes. It seems that the need for a great number of capabilities is common among soil bacteria irrespective of their phylogenetic relationship. However, this would not be possible if soil bacteria lacked indigenous abilities to exchange and accumulate genetic information. The latter are considerably facilitated when housekeeping genes are physically separated from adaptive loci which are useful only in certain circumstances.
2
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Alteration of O-specific polysaccharide structure of symbiotically defective Mesorhizobium loti mutant 2213.1 derived from strain NZP2213

100%
Turska-Szewczuk A., Pietras H., Borucki W., Russa R.
Acta Biochimica Polonica
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2008
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vol. 55
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issue 1
191-200
EN
Mesorhizobium loti mutant 2213.1 derived from the wild-type strain NZP2213 by Tn5 mutagenesis showed impaired effectiveness of symbiosis with the host plant Lotus corniculatus (Turska-Szewczuk et al., 2007 Microbiol Res, in press). The inability of lipopolysaccharide (LPS) isolated from the mutant 2213.1 strain or de-O-acetylated LPS of the parental cells to inactivate phage A1 particles implicated alterations in the LPS structure. The O-specific polysaccharide of the mutant was studied by chemical analyses along with 1H and 13C NMR spectroscopy, which clearly confirmed alterations in the O-chain structure. 2D NMR data showed that the mutant O-polysaccharide consists of a tetrasaccharide repeating unit containing non-substituted as well as O-acetylated or O-methylated 6-deoxytalopyranose residues. Additionally, an immunogold assay revealed a reduced number of gold particles on the mutant bacteroid cell surface, which could result from both a diminished amount of an O-antigenic determinant in mutant LPS and modifications of structural epitopes caused by alterations in O-acetylation or O-methylation of sugar residues. Western immunoblot assay of alkaline de-O-acetylated lipophilic M. loti NZP2213 LPS showed no reactivity with homologous serum indicating a role of O-acetyl groups in its O-specificity.
3
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Straight and branched (ω-1)-hydroxylated very long chain fatty acids are components of Bradyrhizobium lipid A

100%
Choma A., Komaniecka I.
Acta Biochimica Polonica
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2011
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vol. 58
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issue 1
51-58
EN
Lipopolysaccharides of seven Bradyrhizobium strains and three whole-cell fatty acid preparations from bacteria isolated from nodules of Sarothamnus scoparius (Common Broom) were studied for the presence of very long chain (ω-1)-hydroxy fatty acids. Several such fatty acids were identified. Among them, straight-chain as well as mono- and dimethyl branched acids with chains in the range from 26 to 34 carbon atoms were found. Pyrrolidides and 4,4-dimethyloxazoline derivatives were used to determine the branching position. Carbons at the (ω-10) and/or (ω-11) positions in alkyl chains were points of attachment of methyl groups. These data complete the structure of bradyrhizobial lipid A with important details. The obtained results can be applied in the chemotaxonomy of Bradyrhizobium.
4
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Effects of inoculation with mycorrhizae and the benefits of bacteria on physicochemical and microbiological properties of soil, growth, productivity and quality of table grapes grown under Mediterranean climate conditions

86%
Ed-dine S. S., Aberkani K., Said M., Haboubi K., Ghazal H., Ed-dine S. S., Aberkani K., Said M., Haboubi K., Ghazal H.
Journal of Plant Protection Research
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2021
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vol. 61
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issue 4
5
Content available remote

nod Genes and Nod signals and the evolution of the rhizobium legume symbiosis.

86%
Debellé F., Moulin L., Mangin B., Dénarié J., Boivin C.
Acta Biochimica Polonica
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2001
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vol. 48
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issue 2
359-365
EN
The establishment of the nitrogen-fixing symbiosis between rhizobia and legumes requires an exchange of signals between the two partners. In response to flavonoids excreted by the host plant, rhizobia synthesize Nod factors (NFs) which elicit, at very low concentrations and in a specific manner, various symbiotic responses on the roots of the legume hosts. NFs from several rhizobial species have been characterized. They all are lipo-chitooligosaccharides, consisting of a backbone of generally four or five glucosamine residues N-acylated at the non-reducing end, and carrying various O-substituents. The N-acyl chain and the other substituents are important determinants of the rhizobial host specificity. A number of nodulation genes which specify the synthesis of NFs have been identified. All rhizobia, in spite of their diversity, possess conserved nodABC genes responsible for the synthesis of the N-acylated oligosaccharide core of NFs, which suggests that these genes are of a monophyletic origin. Other genes, the host specific nod genes, specify the substitutions of NFs. The central role of NFs and nod genes in the Rhizobium-legume symbiosis suggests that these factors could be used as molecular markers to study the evolution of this symbiosis. We have studied a number of NFs which are N-acylated by α,β-unsaturated fatty acids. We found that the ability to synthesize such NFs does not correlate with taxonomic position of the rhizobia. However, all rhizobia that produce NFs such nodulate plants belonging to related tribes of legumes, the Trifolieae, Vicieae, and Galegeae, all of them being members of the so-called galegoid group. This suggests that the ability to recognize the NFs with α,β-unsaturated fatty acids is limited to this group of legumes, and thus might have appeared only once in the course of legume evolution, in the galegoid phylum.
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