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In recent years, bio-healing based on microbial induced carbonate precipitation in cracks has been widely exploited to improve concrete properties and thus increase its durability. In this context, the present study aims to explore the possibility of using nine bacterial isolates as biohealing agent of cementitious materials; these bacteria (coded B1 to B8) were obtained from the three different rocky sites, i.e., 795 L1 (limestone rock site), 795 L2 (ordinary soil site), and 812 (clayey site); situated in Oulad Rahmoun (Constantine-Algeria). The primary identification showed that eight isolates belonged to a Bacillus genus, and one isolate B8 developed particularly morphological characterized by branched and septate hyphae. The isolates B4 and B8 were selected for their ability to produce calcium carbonate in precipitate calcium (PC) liquid and solid media after five days of incubation. The addition of urea in PC liquid media accelerated the formation of calcite which appeared after 3 days of incubation. The growth curve of both selected isolates on LB liquid medium showed that B8 was characterized by a long exponential growth phase (up to 72 hours) compared to B4 which had an exponential phase up to 48 hours, which could explain the largest amount of calcite precipitate observed in the case of B8 cultivated in PC liquid medium. Results of the bio-healing experiment carried on cementitious batches showed that a beginning of a slight repair of the cracks from the 11th day was only observed in the case of the bacterium B8 but the bio-healing capacity was absent in the control. This bio-healing agent was identified as Micromonospora echinospora (NCBI-NO139612), according to N-Blast of 16S-DNA sequence. In conclusion, the present study is the first to isolate M. echinospora species from rocky sites; and to describe it as an efficient bacterial agent in concrete bio-healing applications. [ABSTRACT FROM AUTHOR]

Fengycin antibiotic displays a strong antifungal activity and inhibits the growth of a wide range of plant pathogens especially filamentous fungi. The main objective of the present study is to characterize fengycin variants produced by B. amyloliquefaciens strain (ET). LC–MS analysis of fengycin extracts has shown several molecular ion peaks corresponding to conventional fengycin homologues (MH + : m/z 1463.9; 1491.9; 1506) and some new ones (MH + : m/z 1433; 1447; 1461; and 1477). Further characterization of these precursor ions was carried out by LC–MS.MS analysis. Reporter fragment ions were observed (named A and B), they correspond to the cleavage of Orn2-Tyr3 (A), Glu1-Orn2 (B), and used for identifying fengycin variants. The reporter fragment couple ions [A/B] at [m/z 966.5/1080.5] and [m/z 994.4 /1108.5] represent fengycin A and B, respectively. The diagnostic ions at ([m/z 980/1094]) may correspond to fengycin C3, D, S or B2. Interestingly, unknown diagnostic product ions at [m/z 951/1065] and [m/z 979/1093] were detected for the first time in this study which prove that they correspond to new fengycin variants, named fengycin X and fengycin Y, respectively. The fengycin X results from a substitution of the glutamine amino acid (Q), at position 8 of the fengycin A peptide part, by an isoleucine (I) or a leucine (L) residue. This mutation should be the same in fengycin Y but compared to fengycin B. [ABSTRACT FROM AUTHOR]

This report is to our knowledge the first to study plant growth promotion and biocontrol characteristics of Bacillus isolates from extreme environments of Eastern Algeria. Seven isolates of 14 (50 %) were screened for their ability to inhibit growth of some phytopathogenic fungi on PDA and some roots exudates. The bacteria identification based on 16S r-RNA and gyrase-A gene sequence analysis showed that 71 % of the screened isolates belonged to Bacillus amyloliquefaciens and the rest were closely related to B. atrophaeus and B. mojavensis. Most of them had high spore yields (22 × 10(8)-27 × 10(8) spores/ml). They produced protease and cellulase cell wall-degrading enzymes while the chitinase activity was only observed in the B. atrophaeus (6SEL). A wide variety of lipopeptides homologous was detected by liquid chromatography-electrospray ionization-mass spectrometry analysis. Interestingly, some additional peaks with new masses were characterized, which may correspond to new fengycin classes. The isolates produced siderophores and indole-3- acetic acid phytohormone. The greenhouse experiment using a naturally infested soil with Sclerotonia sclerotiorum showed that the B. atrophaeus (6SEL) significantly increased the size of the chickpea plants and reduced the stem rot disease (P < 0.05). These results suggest that these isolates may be used further as bio-inoculants to improve crop systems.