1,721,026 research outputs found
A possibile role of nirK in Rhizobium sullae HCNT1.
No full textIn response to a number of environmental stresses many bacterial species, including Vibrio
vulnificus, Sinorhizobium meliloti, Micrococcus luteus, Escherichia coli and Helicobacter pylori,
enter the viable-but-not-culturable (VBNC) status (McDougald et al., 1998). In this metabolic state
they lose their ability to grow on media that usually sustain them and undergo such physiological
and morphological changes as increased resistance to several physic and chemical factors, and
changes in protein and lipid content. The recent increasing use of specific fluorescent dyes such as
Syto 9, CTC (5-cyano-2,3-di-4-tolyl-tetrazolium chloride), AO (Acridine Orange), propidium
iodide, made possible a proper identification of viability and the metabolic state of microbes
(Basaglia et al. 1997).
Sinorhizobium meliloti 41, a rhizobium nodulating Medicago sativa, enters VBNC status in
liquid microcosms when O2 is depleted from the atmosphere of the incubation mixture (Toffanin et
al., 2000; Casella et al. 2001). Plasmid-borne, firefly-derived, luciferase gene (luc) was inserted and
stably inherited in Sinorhizobium meliloti 41 (pRP4-luc) as a reporter gene. The strain obtained, S.
meliloti 41 pRP4-luc and its parental strain, served as a model system for VBNC experiments both
in vitro and in soil samples.
Rhizobium sullae, formerly Rhizobium ’hedysari’, is a nitrogen fixing bacterium that induces
symbiotic nodule formation on the legume Hedysarum coronarium (Squartini et al., 2002). Strain
HCNT1, expressing a copper-containing nitrite reductase encoded by nirK, which is closely related
to nitrite reductases in true denitrifiers, enters the same VBNC status when oxygen is limiting, but
only when nitrite is present and converted to NO. Since HCNT1 cannot grow as a denitrifier and
inactivation of nirK only resulted in the loss of NO production (Toffanin et al, 1996), the hypothesis
that expression of nirK may induce the VBNC status has been investigated.
Therefore, a comparison between the two systems, S. meliloti and R. sullae, is presented in order
to verify the possible connection of nirK with the VBNC status.
McDougald D. et al. 1998. FEMS Microbiology Ecology 25: 1-9
Basaglia M. et al. 1997. In: The biotechnology and ecological interactions of microbial inoculants".
Granada, Spain. pp. 19-20
Toffanin A. et al. 2000. Biol. Fertil. Soils. 31 (6): 484-488
Casella S. et al. 2001. ISME-9, Amsterdam (The Netherlands), p. 191
Squartini A. et al. 2002. Int. J. Syst. Evol. Microbiol. 52: 1267-1276
Toffanin A. et al. 1996. Appl. Environ. Microbiol. 62 (11): 4019-402
The influence of Azospirillum baldaniorum Sp245 on cutting propagation and plant growth after transplantation in olive Leccino cultivar (Olea europaea L.).
Full text linkThe employment of plant growth promoting bacteria (PGPB) is a developing practice mainly involved under organic agricultural contexts. In particular, the use of alternative rooting agents may successfully contribute to the development of the olive sector propagation. This issue has let to assess the potential effect of the free-living soil bacteria Azospirillum baldaniorum Sp245 on olive cultivar ‘Leccino’ as i) root inductor for cuttings and ii) biostimulant on growth of nursery olive young plants. During the first nursery phase related to the rooting inductive process, comparative analyses were carried out between A. baldaniorum Sp245 and indole-3-butyric acid (IBA), a synthetic auxin usually used as root-promoting compound. Moreover, the bacterial suspension was periodically applied to the growing medium of hardened young plants, and compared with treatments by cell-free supernatant derived from the bacterial culture. Positive results were obtained on the assessment of the early histological changes related to the adventitious root formation. Interestingly, similar responses between cuttings treated with A. baldaniorum Sp245 and IBA were observed. Young plants provided with the bacterial suspension showed a general growing improvement of both hypogeal and epigeal apparatus. These features suggest that A. baldaniorum Sp245 could be usefully employed as rooting inducer, promoting a possible IBA replacing. Moreover, the improved quality of young olive plants determined by A. baldaniorum Sp245 supply, make it a profitable biostimulant in a context of organic nursery systems
Young adult migrants’ representation of ethnic, gender and generational disadvantage in Italy*
No full textThe literature on the division of labour and labour market segmentation has generally stressed that young people and migrants are, for different reasons, the most disadvantaged categories of workers. Faced with these inequalities, numerous studies have investigated how young people represent and understand their social disadvantage. Similar research on migrant workers is very limited, however, especially as regards young migrants. This article aims to contribute to filling this gap. Our goal is to examine how young adult migrants represent their experiences of ethnic, gender and generational disadvantage and discrimination in the occupational domain. The paper is based on an analysis of in-depth interviews conducted with young adult migrants of Moroccan and Romanian origin living in the Veneto region of Italy
Azospirillum baldaniorum Sp245 Induces Anatomical Changes in Cuttings of Olive (Olea europaea L., cultivar Leccino): Preliminary Results.
Full text linkMicrobes as biostimulants in Mediterranean plants: the effect of Azospirillum baldaniorum Sp245 in cuttings of olive (Olea europaea L., cultivar Leccino)
No full text
Cell surface lipopolysaccharides of different rhizobia.
No full textPolyacrylamide gel electrophoresis profiles of various cell surface lipopolysaccharides (LPS) obtained from fast-growing strains and plasmidless mutant strains of Rhizobium ‘hedysari’, R. leguminosarum and from slow-growing Bradyrhizobium japonicum strains have been compared. Correlations were obtained by using serological techniques.
Two of the fast-growing strains and one slow-growing strain employed showed several LPS with slow mobility and a few others characterized by fast mobility in the gel. Other fast-growing rhizobium strains and all the other slow-growing bradyrhizobia tested had bands widely distributed in the gels. Location of bands, in these rhizobia, did not correlate with rapidity of growth of the strains.
Induced antibiotic resistance did not affect LPS composition for either the fast- or slow-growing rhizobia. The LPS composition was apparently affected by the loss of plasmids. It appears to be associated with the lack of some bands in the region ranging from 30–50 kDa.
The LPS composition was also affected by the mutation in the fast mobility region. The mutant strain lacked a low molecular mass band compared with the parental strain. [1H]-NMR spectra of LPS extracts from the latter strain also revealed a signal that is missing from the spectrum of the LPS of mutant strain
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