Classical methods for protein extraction from microorganisms, used for large-scale treatments such as mechanical or chemical processes, affect the integrity of extracted cytosolic protein by releasing proteases contained in vacuoles. Our previous experiments on flow-process yeast electroextraction proved that pulsed electric field technology allows us to preserve the integrity of released cytosolic proteins by keeping intact vacuole membranes. Furthermore, large volumes are easily treated by the flow technology. Based on this previous knowledge, we developed a new protocol in order to electroextract total cytoplasmic proteins from microalgae (Nannochloropsis salina and Chlorella vulgaris). Given that induction of electropermeabilization is under the control of the target cell size, as the mean diameter for N. salina is only 2.5 μm, we used repetitive 2-ms-long pulses of alternating polarities with stronger field strengths than previously described for yeasts. The electric treatment was followed by a 24-h incubation period in a salty buffer. The amount of total protein released was evaluated by a classical Bradford assay. A more accurate evaluation of protein release was obtained by SDS-PAGE. Similar results were obtained with C. vulgaris under milder electrical conditions, as expected from their larger size. This innovative technology designed in our group should become familiar in the field of microalgae biotechnology.

SummaryErwinia amylovora causes fire blight on several plant species such as apple and pear, which produce diverse phytoalexins as defence mechanisms. An evolutionary successful pathogen thus must develop resistance mechanisms towards these toxic compounds. The E. amylovora outer membrane protein, TolC, might mediate phytoalexin resistance through its interaction with the multidrug efflux pump, AcrAB. To prove this, a tolC mutant and an acrB/tolC double mutant were constructed. The minimal inhibitory concentrations of diverse antimicrobials and phytoalexins were determined for these mutants and compared with that of a previously generated acrB mutant. The tolC and arcB/tolC mutants were considerably more susceptible than the wild type but showed similar levels as the acrB mutant. The results clearly indicated that neither TolC nor AcrAB significantly interacted with other transport systems during the efflux of the tested toxic compounds. Survival and virulence assays on inoculated apple plants showed that pathogenicity and the ability of E. amylovora to colonize plant tissue were equally impaired by mutations of tolC and acrB/tolC. Our results allowed the conclusion that TolC plays an important role as a virulence and fitness factor of E. amylovora by mediating resistance towards phytoalexins through its exclusive interaction with AcrAB.

In the plant pathogenic bacterium, Pseudomonas syringae, the exopolysaccharide levan is synthesized by extracellular levansucrase (Lsc), which is encoded by two conserved 1,296-bp genes termed lscB and lscC in P. syringae strain PG4180. A third gene, lscA, is homologous to the 1,248-bp lsc gene of the bacterium Erwinia amylovora, causing fire blight. However, lscA is not expressed in P. syringae strain PG4180. Herein, PG4180 lscA was shown to be expressed from its native promoter in the Lsc-deficient E. amylovora mutant, Ea7/74-LS6, suggesting that lscA might be closely related to the E. amylovora lsc gene. Nucleotide sequence analysis revealed that lscB and lscC homologs in several P. syringae strains are part of a highly conserved 1.8-kb region containing the ORF, flanked by 450-452-bp and 49-51-bp up- and downstream sequences, respectively. Interestingly, the 450-452-bp upstream sequence, along with the initial 48-bp ORF sequence encoding for the N-terminal 16 amino acid residues of Lsc, were found to be highly similar to the respective sequence of a putatively prophage-borne glycosyl hydrolase-encoding gene in several P. syringae genomes. Minimal promoter regions of lscB and lscC were mapped in PG4180 by deletion analysis and were found to be located in similar positions upstream of lsc genes in three P. syringae genomes. Thus, a putative 498-500-bp promoter element was identified, which possesses the prophage-associated com gene and DNA encoding common N-terminal sequences of all 1,296-bp Lsc and two glycosyl hydrolases. Since the gene product of the non-expressed 1,248-bp lscA is lacking this conserved N-terminal region but is otherwise highly homologous to those of lscB and lscC, it was concluded that lscA might have been the ancestral lsc gene in E. amylovora and P. syringae. Our data indicated that its highly expressed paralogs in P. syringae are probably derived from subsequent recombination events initiated by insertion of the 498-500-bp promoter element, described herein, containing a translational start site.

Worldwide, peptic ulcer and gastritis considered to be one of the biggest health challenge, Helicobacter pylori is responsible for more than eighty percent of chronic active gastritis where continual infection remains for decennary. However, the success of commercially available drugs for the management of H. pylori has overwhelmed by antibiotic-resistant strains, especially, metronidazole and clarithromycin, therefore, an urgent need arise to search for new options for treatment with enhanced anti-H. pylori activities, while being less toxic to human cells. Naturally occurring plant products, including spices, are one of these strategies that showed activity against H.pylori. Present study aim to test the antibacterial activity of capsaicin and other pure plant-derived compounds against a standard (NCTC 11916) H. pylori strain In vitro and to test for possible synergistic effect when combined with conventional therapy. Capsaicin shows good antibacterial activity on regular antimicrobial sensitivity testing methods (Anti-MSTM) and titration checkerboard assay MIC (0.0625 mg/ml), whereas piperine MIC was (0.125 mg/ ml). While for curcumin no inhibition was found. The strain was found to be resistant to metronidazole with (MIC=250 μg/ml). When combining capsaicin with metronidazole, (FIC) Fractional inhibitory concentration values shown a synergistic effect, While the additive effect was found for capsaicin combination with piperine. Our obtained data indicate that capsaicin possesses promising anti H.pylori bioactivity and synergistic activity when combined with metronidazole but more work is necessary to examine the mechanisms by which these happened. Furthermore, it is necessary to ensure its activity against H.pylori In vivo and clinical settings.

AcrAB-TolC is the major multidrug efflux system in Enterobacteriaceae recognizing structurally unrelated molecules including antibiotics, dyes, and detergents. Additionally, in Escherichia coli it mediates resistance to bile salts. In the plant pathogen Erwinia amylovora AcrAB-TolC is required for virulence and phytoalexin resistance. Exchange analysis of AcrAB-TolC was conducted by complementing mutants of both species defective in acrB or tolC with alleles from either species. The acrB and tolC mutants exhibited increased susceptibility profiles for 24 different antibiotics. All mutants were complemented with acrAB or tolC, respectively, regardless of the taxonomic origin of the alleles. Importantly, complementation of E. amylovora mutants with respective E. coli genes restored virulence on apple plants. It was concluded that AcrAB and TolC of both species could interact and that these interactions did not yield in altered functions despite the divergent ecological niches, to which E. coli and E. amylovora have adopted.