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Non-specific nuclease (NSN) can be applied in industrial downstream processing to remove nucleic acids from crude protein extracts or in cell-sorting systems to degrade nucleic acids derived from lysed cells. Ps Nuc from the ice-nucleating bacterium Pseudomonas syringae has the ability to decompose double- and single-stranded DNA in linear or circular form and RNA. It is not affected by the presence of metal-ion chelators such as EDTA and tolerates several protease inhibitors and reducing agents. A multiple sequence alignment of Ps Nuc with closely related enzymes (97–99% identity on the protein level) within the family Pseudomonaceae revealed the presence of only six amino acid residues that are variable in putative NSN from different members of the genus Pseudomonas . Single amino acid variants were produced in recombinant form in Escherichia coli , purified, and characterized. They showed similar activity compared to Ps Nuc, but a single variant even displayed an improved performance with an activity of > 20,000 U/mg at 35 °C, while amino acid residues S148 and V161 were found to be essential for enzymatic functionality. These results suggest that homologous nucleases from Pseudomonaceae display high activity levels in a metal-ion-independent manner and are therefore of interest for applications in biotechnology.

In natural environment, semiochemicals are involved in many interactions between the different trophic levels involving insects, plants and hosts for parasitoids or prey for predators. These volatile compounds act as messengers within or between insect species, inducing particular behaviours, such as the localisation of a source of food, the orientation to an adequate oviposition site, the selection of a suitable breeding site and the localisation of hosts or prey. In this sense, bacteria have been shown to play an important role in the production of volatile compounds which ones act as semiochemicals. This review, focusing on the semiochemically mediated interactions between bacteria and insects, highlights that bacterial semiochemicals act as important messengers for insects. Indeed, in most of the studies reported here, insects respond to specific volatiles emitted by specific bacteria hosted by the insect itself (gut, mouthparts, etc.) or present in the natural environment where the insect evolves. Particularly, bacteria from the families Enterobacteriaceae, Pseudomonaceae and Bacillaceae are involved in many interactions with insects. Because semiochemicals naturally produced by bacteria could be a very interesting option for pest management, advances in this field are discussed in the context of biological control against insect pests.

The adaptive flexibility of bacteria largely contributes to the emergence of antibiotic resistance, eventually leading to the predictable failure of current antimicrobial therapies. It is of utmost importance to improve current approaches and implement new ways to control bacterial growth and proliferation. A promising strategy lies in unraveling the antimicrobial resistance (AMR) dynamics in environmental reservoirs, namely in soil. Environmental microorganisms are antibiotic producers and generally also carriers of AMR mechanisms. Therefore, soil samples were collected from areas distinctly influenced by men: rural farms and urban fluvial shores. Globally, microbial communities collected in farms revealed the highest antibiotic resistance potential. Largely predominant Gram-negative isolates were further screened for their low susceptibility to β-lactamic agents, and found to belong to Pseudomonaceae family, with predominance of Pseudomonas putida (92 %). Minimal Inhibitory Concentration (MIC) was determined for five β-lactams and the distributive analysis of cefotaxime MIC performed, allowing the first report of Epidemiological Cut-OFF values for P. putida regarding such antibiotic. Hence, 46 % of the isolates from farms presented acquired resistance to cefotaxime, with fluvial strains presenting an acquisition of AMR in 22 % of the isolates. The response to β-lactams impact in P. putida is different from Pseudomonas aeruginosa ’s, the family type strain, showing that data determined for a species should only be extended to other bacteria with caution, even closely related. It becomes crucial to broaden present research, mainly focused on few pathogenic bacteria, to other microorganisms carrying relevant resistance tools or capable of genetic transfer to more virulent strains. Most available data on AMR so far has been obtained from studies performed in restricted clinical or veterinary context, showing the result of a strong selective pressure related to therapy but often disregarding the origin of the AMR mechanisms encountered. The strong impact that environmental microorganisms have (and probably already had in the past) on the evolution and spreading of AMR, is just beginning to be unveiled.

Resistance in tomato to the bacterial pathogen Pseudomonas syringae pathovar tomato requires Pto and Prf. Mutations that eliminate Prf show a loss of both Pto resistance and sensitivity to the organophosphate insecticide fenthion, suggesting that Prf controls both phenotypes. Herein, we report that the overexpression of Prf leads to enhanced resistance to a number of normally virulent bacterial and viral pathogens and leads to increased sensitivity to fenthion. These plants express levels of salicylic acid comparable to plants induced for systemic acquired resistance (SAR) and constitutively express pathogenesis related genes. These results suggest that the overexpression of Prf activates the Pto and Fen pathways in a pathogen-independent manner and leads to the activation of SAR. Transgene-induced SAR has implications for the generation of broad spectrum disease resistance in agricultural crop plants

Recently upwelled water from the southern Benguela upwelling system was incubated in a 60 l microcosm for 43 d under simulated in situ conditions, to follow the development and activity of the heterotrophic microplanktonic community associated with phytoplankton growth and decay. The initial bacterial population (40 μg C l⁻¹), dominated by small rods (v̄ = 0.198 μm³) and large cocci (v̄ = 0.142 μm³), with Vibrionaceae as the dominant plateable strain, exhibited slow turnover times for added ¹⁴C-labelled substrates (x̄ = 5.7 h 10⁶ cells⁻¹). Net bacterial growth was exponential (0.016 h⁻¹) during phytoplankton growth (12 μg C l⁻¹ h⁻¹, Days 0 to 4). At maximum phytoplankton and bacterial biomass (1330 and 136 μg C l⁻¹ respectively, Day 4) Pseudomonadaceae dominated the plateable isolates; bacterial turnover times for ¹⁴C-substrates were rapid (glucose: 1.5 h 10⁶ cells⁻¹, alanine: 0.49 h 10⁶ cells⁻¹, glutamate: 0.29 h 10⁶ cells⁻¹), suggesting a close coupling between phytoplankton growth and the ability of bacteria to utilise dissolved organic carbon (PDOC) substrates. Bacterial biomass was reduced to <15 μg C l⁻¹ by Day 9, due to diminished availability of PDOC during phytoplankton senescence and predation by microflagellates which developed in the microcosm (<5 μg C l⁻¹ up to Day 4, 96 μg C l⁻¹ on Day 8). After phytoplankton senescence (Day 10) detrital carbon stimulated exponential growth (0.021 h⁻¹) of a second bacterial community (max. biomass: 231 μg C l⁻¹ on Day 25) dominated by small cocci (v̄ = 0.009 μm³) and large rods (v̄ = 0.672 μm³), with Flavobacteriaceae as the dominant plateable bacteria. As this community exhibited no uptake of added ¹⁴C-labelled substrates, we surmise that it was exploiting POC which dominated carbon resources at this time. Estimates of bacterial production calculated from net growth rates were ca 50 to 97 % higher than values based on [methyl-³H] thymidine incorporation (TTI). These differences may be due to inadequate DNA extraction procedures, large numbers of bacteria without thymidine transport systems, or isotope dilution. Empirically determined conversion factors to correct for these differences fell within the range of 1.6 to 46 × 10⁶ cells mol⁻¹ TTI.

Shoots of \"San Castrese\" and \"Portici\" apricots (Prunus armeniaca L.) free of cultivable bacteria, shoots of the same origin exhibiting bacterial contamination after repeated subcultures, and contaminated shoots treated with cefotaxime were compared for gas exchange, proliferation rate, and fresh and dry weight. Cultures of San Castrese contaminated by Bacillus circulans and Sphingomonas paucimobilis, and of Portici contaminated with Staphylococcus hominis and Micrococcus kristinae, including those treated with cefotaxime, showed comparable shoot weights and lower proliferation rates than healthy cultures. Bacteria, even if not visible until the end of subculture, markedly influenced the gaseous composition of the jar headspace. Healthy cultures clearly showed photosynthetic activity at$60\\mu M\\cdot \\text{m}^{-2}\\cdot \\text{s}^{-1}$photosynthetically active radiation; in contrast, oxygen quickly decreased and carbon dioxide increased in contaminated cultures, including those treated with cefotaxime, in which bacteria became visible in the culture medium only after repeated subcultures.