There is growing interest in the use of bio inoculants based on plant growth-promoting bacteria (PGPB) to promote plant growth under biotic and abiotic stresses. Here, we provided a detailed account of the effectiveness of a number of endophytic PGPB strains, isolated from the roots of the halophyte Salicornia brachiata in promoting durum wheat growth and enhancing its tolerance to salinity and fusarium head blight (FHB) disease. Bacillus spp. strains MA9, MA14, MA17, and MA19 were found to have PGPB characteristics as they produced indole-3-acetic acid, siderophores, and lytic enzymes, fixed free atmospheric nitrogen, and solubilized inorganic phosphate in vitro. Additionally, the in vivo study that involved in planta inoculation assays under control and stress conditions indicated that all PGPB strains significantly (p < 0.05) increased the total plant length, dry weight, root area, seed weight, and nitrogen, protein, and mineral contents. Particularly, the MA17 strain showed a superior performance since it was the most efficient in reducing disease incidence in wheat explants by 64.5%, in addition to having the strongest plant growth promotion activity under salt stress. Both in vitro and in vivo assays showed that MA9, MA14, MA17, and MA19 strains were able to play significant PGPB roles. However, biopriming with Bacillus subtilis MA17 offered the highest plant growth promotion and salinity tolerance, and bioprotection against FHB. Hence, it would be worth testing the MA17 strain under field conditions as a step towards its commercial production. Moreover, the strain could be further assessed for its plausible role in bioprotection and growth promotion in other crop plants. Thus, it was believed that the strain has the potential to significantly contribute to wheat production in arid and semi-arid regions, especially the salt-affected Middle Eastern Region, in addition to its potential role in improving wheat production under biotic and abiotic stresses in other parts of the world.

Bacteriophages could be a useful adjunct to antibiotics for the treatment of multidrug-resistant Pseudomonas aeruginosa infections. In this study, lytic P. aeruginosa myoviruses PsCh, PsIn, Ps25, and Ps12on-D were isolated from Tunisian sewage samples. Phage Ps12on-D displayed an adsorption time of ~10 min, a short latency period (~10 min), and a large burst size (~115 PFU per infected cell) under standard growth conditions. All phages were active at broad temperature (4 °C to 50 °C) and pH (3.0 to 11.0) ranges and were able to lyse a wide variety of P. aeruginosa strains isolated from clinical and environmental samples worldwide. Illumina sequencing revealed double-stranded DNA genomes ranging from 87,887 and 92,710 bp with high sequence identity to Pseudomonas phage PAK_P1. All four phages based on sequence analysis were assigned to the Pakpunavirus genus. The presented characterization and preclinical assessment are part of an effort to establish phage therapy treatment as an alternative strategy for the management of multidrug-resistant P. aeruginosa infections in Tunisia.

Newly discovered Erwinia amylovora phages PEar1, PEar2, PEar4 and PEar6 were isolated from three different orchards in North Tunisia to study their potential as biocontrol agents. Illumina sequencing revealed that the PEar viruses carry a single-strand DNA genome between 6608 and 6801 nucleotides and belong to the Inoviridae, making them the first described filamentous phages of E. amylovora. Interestingly, phage-infected cells show a decreased swimming and swarming motility and a cocktail of the four phages can significantly reduce infection of E. amylovora in a pear bioassay, potentially making them suitable candidates for phage biocontrol.

A number of newly isolated halophilic microorganisms were screened for protease production. A bacterium designated as strain SBJ9 showed an important enzyme production at high salt concentrations and was then retained. The 16S DNA identification put this strain in the genus of Salicola with two reference species only. Protease production was higher at salinities ranging from 150 to 200 g/l (3.2 M) NaCl, when monitored at 35 °C and pH 7. The protease activity was optimal at 2.5 MNaCl, 40°C and pH 8, with high stability at wide ranges of salinity (1-5 MNaCl), temperatures (20- 70 °C) and pH values (5- 11). It was slightly improved by 5 mM CaCl₂ and totally inhibited by PMSF which indicated the dominance of serine proteases. Besides, it was perfectly stable in the presence of many detergent additives and organic solvents at high concentrations. These important features make Salicola sp. strain SBJ9 protease activity a good candidate for many industrial applications such as detergency and organic synthesis.

Attributed to a Gram-negative bacterium, identified as Erwinia amylovora, the fire blight disease, recently detected in Tunisia, has become a real threat to our economy and our arboriculture.There is no effective curative treatment to eliminate the installed bacterium. It is therefore essential to prevent attacks and to limit the spread of the bacteria if it is already present. To do so we have chosen the biocontrol by bacteriophages. In this work we have isolated new strains of Erwinia amylovora (10 strains) from plant tissues where fire blight symptoms are persistent. These strains have been the subject of a molecular study. The isolated phages (30 isolates) were studied for their infectivity on Erwinia amylovora isolates and showed a surprising effect. Our phage isolates formed plaque of different sizes, with a diameter ranging between 0.5 and 2mm on the soft agar layer containing the test bacterium. The phages thermostability showed that all these viruses resist at 80 ° C for 45 min

Salinity is one of the most severe abiotic stresses limiting crop yield. Salt-affected area in Tunisia is fast escalating due to intrusion of saline water on arable land and use of chemical fertilizers and pesticides. Thus, a great effort is required to preserve crop production under limiting factors. The present study was conducted to isolate and identify PGPB associated with two halophyte plants from coastal saline site. These strains were tested for improved crop productivity under salinity conditions. Four strains namely MA9, MA14, MA17 and MA19 were selected The PGPB-inoculated plants were relatively healthy and hydrated, whereas the uninoculated plant leaves were desiccated in the presence of 125 mM NaCl. The percentage of water content (PWC) in the plant was also significantly higher in inoculated plants compared to uninoculated ones. Under greenhouse experiments, our data revealed that experiments using seed biopriming on non-sterile soil supplemented with NaCl permitted to identify the most efficient isolates which offered the best vegetable criteria by significantly increasing root and shoot length, root and shoot dry weights, area of the root system and thousand seed mass in plant growth trials. The benefic effect of seed biopriming was more pronounced in soil samples added with NaCl than that of untreated soil. Seed biopriming by efficient PGPB strains induced salinity tolerance of wheat and therefore enhanced their productivity under salinity.