Synthesis, Crystal Structure and Antimicrobial Properties of 1-Diphenylmethylpiperazine-1,4-Diium Tetrachloridocuprate

New organic/inorganic hybrid (C17H22N2)[CuCl4] was elaborated and studied by single crystal X-ray diffraction. The compound crystallizes in the orthorhombic Pbca space group. The isolated [CuCl4]2- tetrahedra are slightly distorted building a 0-D anionic framework. The double protonation of the organic cation establish N—H···Cl interactions between organic and inorganic moieties leading to self-organized structure. Infrared, UV-Visible and photoluminescence studies were carried out. The in-vitro antibacterial and antifungal activity of the title salt against several microorganisms were studied. The purity of the material was controlled by Rietveld analysis based on structural investigations and X-ray powder diffraction

Halocins, Bacteriocin-Like Antimicrobials Produced by the Archaeal Domain: Occurrence and Phylogenetic Diversity in <em>Halobacteriales</em>

Members of extremely halophilic archaea, currently consisting of more than 56 genera and 216 species, are known to produce their specific bacteriocin-like peptides and proteins called halocins, synthesized by the ribosomal pathway. Halocins are diverse in size, consisting of proteins as large as 35 kDa and peptide “microhalocins” as small as 3.6 kDa. Today, about fifteen halocins have been described and only three genes, halC8, halS8 and halH4, coding C8, S8 and H4 halocins respectively have been identified. In this study, a total of 1858 of complete and nearly complete genome sequences of Halobacteria class members were retrieved from the IMG and Genbank databases and then screened for halocin encoding gene content, based on the BLASTP algorithm. A total of 61 amino acid sequences belonging to three halocins classes (C8, HalH4 and S8) were identified within 15 genera with the abundance of C8 class. Phylogenetic analysis based on amino acids sequences showed a clear segregation of the three halocins classes. Halocin S8 was phylogenetically more close to HalH4. No clear segregation on species and genera levels was observed based on halocin C8 analysiscontrary to HalH4 based analysis. Collectively, these results give an overview on halocins diversity within halophilic archaea which can open new research topics that will shed light on halocins as marker for haloarchaeal phylogentic delineation

Pseudomonas aeruginosa Swarmer Cells Adaptation Toward UVc Radiations

Swarming is the most rapid surface motility allowing Pseudomonas aeruginosa bacteria to rapidly colonize new surfaces. However, swarming behavior is affected by environmental factors like ultraviolet irradiation (UVc). UVc radiation is the most disinfection technology usually applied for wastewater and proven to be effective to inactivate microorganisms. However, efficiency against motile bacteria is not yet studied. This study aims to explain the mechanisms of resistance of swarmer P. aeruginosa cells toward UVc exposure. P. aeruginosa liquid cultures were allowed to swarm across a semisolid surface for 18 h and directly exposed to UVc radiations. Emergent swarmer colonies, revealed after re-incubation, were selected to study biofilm formation, fatty acid (FA) composition, and ultrastructure. Our results showed that membrane adaptation to UVc radiations was seen in Pseudomonas cells by an increase of cyclic fatty acid (CFA) content, confirming the role of cyclopropane in radio-resistance of swarmer cells. Furthermore, electron microscopic study confirmed that over production of S-layer is believed to be a protective form adopted by P. aeruginosa swarmer cells to resist after 5 min of UVc exposure. Moreover, membrane disintegration is the lethal effect observed after 15 min of UVc exposure. In the other hand, study of biofilm production showed an enhancement of biofilm formation, of swarmer cells mainly after 15 min of UVc exposure. There results confirmed that swarming process is highly correlated with particular FA composition of P. aeruginosa membrane and that radio-resistance of swarmer cells is highly supported by CFA biosynthesis and S-layer overproduction

Different Modes of Regulation of the Expression of Dextransucrase in Leuconostoc lactis AV1n and Lactobacillus sakei MN1

Leuconostoc lactis AV1 strain isolated from a Tunisian avocado was characterized as a dextran producer. The promoter PdsrLL and the dsrLL gene encoding the DsrLL dextransucrase responsible for the dextran synthesis were transcriptionally fused to the mCherry coding gene generating the pRCR20 plasmid. Upon plasmid transfer, both AV1n and the dextran non-producing Leuconostoc mesenteroides CM70 became red due to expression of the mCherry from the PdsrLL-dsr-mrfp transcriptional fusion. Characterization of the polymers present in cultures supernatants revealed that the DsrLL encoded from pRCR20 in the recombinant bacteria was able to synthesize dextran. The production of dextran by the DsrLL in AV1n increased in response to low temperature, reaching 10-fold higher levels at 20°C than at 37°C (4.15 g/L versus 0.41 g/L). To analyze if this stress response includes activation at the transcriptional level and if it was only restricted to Leuconostoc, AV1n was transformed with plasmids carrying either the PdsrLL-mrfp fusion or the PdsrLS of Lactobacillus sakei MN1 fused to the mrfp gene, and the influence of temperature and carbon source on expression from the Dsr promoters was monitored by measurement of the mCherry levels. The overall expression analysis confirmed an induction of expression from PdsrLL upon growth at low temperature (20°C versus 30°C and 37°C) in the presence of sugars tested (sucrose, glucose, maltose, and fructose). In addition, the presence of sucrose, the substrate of Dsr, also resulted in activation of expression from PdsrLL. A different behavior was detected, when expression from PdsrLS was evaluated. Similar levels of fluorescence were observed irrespectively of the carbon source or temperature, besides a sequential decrease at 30°C and 20°C, when sucrose was present in the growth medium. In conclusion, the two types of regulation of expression of Dsr presented here revealed two different mechanisms for environmental adaptation of Leuconostoc and Lactobacillus that could be exploited for industrial applications

Aridity modulates belowground bacterial community dynamics in olive tree

Aridity negatively affects the diversity and abundance of edaphic microbial communities and their multiple ecosystem services, ultimately impacting vegetation productivity and biotic interactions. Investigation about how plant-associated microbial communities respond to increasing aridity is of particular importance, especially in light of the global climate change predictions. To assess the effect of aridity on plant associated bacterial communities, we investigated the diversity and co-occurrence of bacteria associated with the bulk soil and the root system of olive trees cultivated in orchards located in higher, middle and lower arid regions of Tunisia. The results indicated that the selective process mediated by the plant root system is amplified with the increment of aridity, defining distinct bacterial communities, dominated by aridity-winner and aridity-loser bacteria negatively and positively correlated with increasing annual rainfall, respectively. Aridity regulated also the co-occurrence interactions among bacteria by determining specific modules enriched with one of the two categories (aridity-winners or aridity-losers), which included bacteria with multiple PGP functions against aridity. Our findings provide new insights into the process of bacterial assembly and interactions with the host plant in response to aridity, contributing to understand how the increasing aridity predicted by climate changes may affect the resilience of the plant holobiont

Microbiological analysis and assessment of biotechnological potential of lactic acid bacteria isolated from Tunisian flours

International audienceThis work was carried out to identify lactic acid bacteria (LAB) from baking wheat flours and to evaluate their technological capabilities for potential incorporation in sourdough process. Six samples of wheat flours obtained from different geographical regions of Tunisia were microbiologically analyzed. Several technological features including acidification, antimicrobial, amylolytic, proteolytic, and antioxidant activities of six selected LAB strains were investigated for future in situ applications. Moreover, LAB were investigated for their ability to produce exopolysaccharides. A total of 45 autochthonous LAB were isolated and identified by genetic analysis of 16S–23S rRNA intergenic transcribed spacer (ITS)-generated patterns ITS-PCR. One of each ITS-PCR pattern was subjected to partial 16S rRNA gene sequencing, and strains were identified as Weissella cibaria, Lactobacillus plantarum, Lactobacillus brevis, Pediococcus pentosaceus, Pediococcus pentoseus, Pediococcus acidilactici, Enterococcus faecium, Enterococcus casseliflavus, and Enterococcus faecalis. All tested LAB showed good acidifying ability by decreasing significantly (p < 0.05) the pH of flour extract below 4.0 after 24 h and below 3.0 after 72 h. Pediococcus pentoseus and P. acidilactici presented fermentation quotient (FQ, ratio of lactic and acetic acids) close to the optimal range. All LAB isolates demonstrated extracellular proteolytic activity. Weissella cibaria S25 had the highest radical-scavenging activity with 25.57%. Lactobacillus plantarum S28 demonstrated the highest amylolytic activity (1386 U/mL) followed by P. acidilactici S16 (1086 U/mL). Although, L. plantarum S28 showed the highest production of exopolysaccharides (0.97 g/L). Moreover, varying halo of inhibition was detected against Escherichia coli, Staphylococcus aureus, Aspergillus niger, and Penicillium expansum. This study revealed that autochthonous flour LAB had interesting technological features and thus could be used in sourdough production

Diversity of vaginal lactic acid bacterial microbiota in 15 Algerian pregnant women with and without bacterial vaginosis by using culture independent method

International audienceBacterial Vaginosis (BV) is the most common lower genital tract disorder among women of reproductive age (pregnant and non-pregnant) and a better knowledge of Lactobacillus species richness in healthy and infected vaginal microbiota is needed to efficiently design better probiotic products to promote the maintenance of normal flora which will help prevent bacterial vaginosis

Functional Probiotic Assessment and In Vivo Cholesterol-Lowering Efficacy of Weissella sp. Associated with Arid Lands Living-Hosts

The research and the selection of novel probiotic strains from novel niches are receiving increased attention on their proclaimed health benefits to both humans and animals. This study aimed to evaluate the functional properties of Weissella strains from arid land living-hosts and to select strains with cholesterol-lowering property in vitro and in vivo, for use as probiotics. They were assessed for acid and bile tolerance, antibiotic susceptibility, membrane properties, antibacterial activity, antiadhesive effect against pathogens to host cell lines, and cholesterol assimilation in vitro. Our results showed that the majority of strains revealed resistance to gastrointestinal conditions. All the strains were nonhemolytic and sensitive to most of the tested antibiotics. They also exhibited high rates of autoaggregation and some of them showed high coaggregation with selected pathogens and high adhesion ability to two different cell lines (Caco-2 and MIM/PPk). Particularly, W. halotolerans F99, from camel feces, presented a broad antibacterial spectrum against pathogens, reduced Enterococcus faecalis and Escherichia coli adhesion to Caco-2 cells, and was found to reduce, in vitro, the cholesterol level by 49 %. Moreover, W. halotolerans F99 was evaluated for the carbohydrate utilization as well as the serum lipid metabolism effect in Wistar rats fed a high-cholesterol diet. W. halotolerans F99 showed an interesting growth on different plant-derivative oligosaccharides as sole carbon sources. Compared with rats fed a high-fat (HF) diet without Weissella administration, total serum cholesterol, low-density lipoprotein cholesterol, and triglycerides levels were significantly (p<0.001) reduced in W. halotolerans F99-treated HF rats, with no significant change in high-density lipoprotein cholesterol HDL-C levels. On the basis of these results, this is the first study to report that W. halotolerans F99, from camel feces, can be developed as cholesterol-reducing probiotic strain. Further studies may reveal their potential and possible biotechnological and probiotic applications

Diversity and Antimicrobial Properties of Lactic Acid Bacteria Isolated from Rhizosphere of Olive Trees and Desert Truffles of Tunisia

A total of 119 lactic acid bacteria (LAB) were isolated, by culture-dependant method, from rhizosphere samples of olive trees and desert truffles and evaluated for different biotechnological properties. Using the variability of the intergenic spacer 16S-23S and 16S rRNA gene sequences, the isolates were identified as the genera Lactococcus, Pediococcus, Lactobacillus, Weissella, and Enterococcus. All the strains showed proteolytic activity with variable rates 42% were EPS producers, while only 10% showed the ability to grow in 9% NaCl. In addition, a low rate of antibiotic resistance was detected among rhizospheric enterococci. Furthermore, a strong antibacterial activity against plant and/or pathogenic bacteria of Stenotrophomonas maltophilia, Pantoea agglomerans, Pseudomonas savastanoi, the food-borne Staphylococcus aureus, and Listeria monocytogenes was recorded. Antifungal activity evaluation showed that Botrytis cinerea was the most inhibited fungus followed by Penicillium expansum, Verticillium dahliae, and Aspergillus niger. Most of the active strains belonged to the genera Enterococcus and Weissella. This study led to suggest that environmental-derived LAB strains could be selected for technological application to control pathogenic bacteria and to protect food safety from postharvest deleterious microbiota

In-vitro characterization of potentially probiotic Lactobacillus strains isolated from human microbiota: interaction with pathogenic bacteria and the enteric cell line HT29

Among the various tests commonly used for selecting probiotic microorganisms, the tolerance to gastrointestinal transit conditions remains being commonly used to evaluate the probiotic potential of the strains. Besides, the adhesion to epithelial cells and the competition with pathogens constitute significant traits for evaluating the colonization ability and functional performance of candidate strains. In this study, a total of 13 lactic acid bacteria strains isolated from human feces were first identified by biochemical tests and 16S rRNA gene sequencing, and then characterized in vitro for their tolerance to gastrointestinal conditions, hemolytic activity, and antibiotics sensibility. The isolates were identified as Lactobacillus fermentum (06), Lactobacillus rhamnosus (04), Lactobacillus plantarum (02), and Lactobacillus salivarius (01). The adhesion to epithelial cells HT29 was shown to be a strain-dependent character. L. fermentum 88 and L. plantarum 9, being the ones showing higher adhesion values. They were further characterized by determining their antimicrobial activity, hydrophobicity, co-aggregation, antioxidant activity, as well as the ability to inhibit the adhesion of pathogens to the human epithelial cell line HT29. Moreover, these two strains were able to reduce the adhesion of Escherichia coli to HT29 cells, although they failed for inhibiting the adhesion of other pathogens such as Cronobacter sakazaki or Salmonella enterica. These results point out the importance of considering the ecological fitness of the strains in selecting probiotic bacteria and the potential of some of the analyzed strains for the development of food products.This work was funded by the Tunisian Ministry of Higher Education and Scientific research (laboratory project LR03ES03) and the Department of Microbiology and Biochemistry of Dairy products, IPLA-CSIC, Spain.Peer reviewe