Genomic and Physiological Characterization of Bacilli Isolated From Salt-Pans With Plant Growth Promoting Features

Abstract

Massive application of chemical fertilizers and pesticides has been the main strategy used to cope with the rising crop demands in the last decades. The indiscriminate use of chemicals while providing a temporary solution to food demand has led to a decrease in crop productivity and an increase in the environmental impact of modern agriculture. A sustainable alternative to the use of agrochemicals is the use of microorganisms naturally capable of enhancing plant growth and protecting crops from pests known as Plant-Growth-Promoting Bacteria (PGPB). Aim of the present study was to isolate and characterize PGPB from salt-pans sand samples with activities associated to plant fitness increase. To survive high salinity, salt-tolerant microbes produce a broad range of compounds with heterogeneous biological activities that are potentially beneficial for plant growth. A total of 20 halophilic spore-forming bacteria have been screened in vitro for phyto-beneficial traits and compared with other two members of Bacillus genus recently isolated from the rhizosphere of the same collection site and characterized as potential biocontrol agents. Whole-genome analysis on seven selected strains confirmed the presence of numerous gene clusters with PGP and biocontrol functions and of novel secondary-metabolite biosynthetic genes, which could exert beneficial impacts on plant growth and protection. The predicted biocontrol potential was confirmed in dual culture assays against several phytopathogenic fungi and bacteria. Interestingly, the presence of predicted gene clusters with known biocontrol functions in some of the isolates was not predictive of the in vitro results, supporting the need of combining laboratory assays and genome mining in PGPB identification for future applications.

Net Charges of the Ribosomal Proteins of the S10 and spc Clusters of Halophiles Are Inversely Related to the Degree of Halotolerance

“…In contrast, an unusual pattern was observed in the proteomes of the non-halotolerant bacteria, such as E. coli and T. thermophilus , and of the moderately halophilic Bacillus sp. RHFB ( 92 ), E. natronophila Z-M001 (cyanobacteria) ( 41 ), and S. roseus ( 46 ). In these strains, while the S10-spc cluster proteins showed net positive charges ( Fig.…”

Specialized Metabolites from the Allelopathic Plant Retama raetam as Potential Biopesticides

“…The phytopathogen S. vesicarium was isolated from pears showing brown spot disease symptoms, sampled in Benevento, Campania, Italy, in 2019, as previously reported [ 1 ]. The strain was stored on Potato Dextrose Agar (PDA) plates in the culture collection of Agriges s.r.l., San Salvatore Telesino, Benevento, Italy (40.93345, 14.65799, 401 m.a.s.l.).…”

“…Since the second half of the 20th century, the agricultural practices have been based on the uncontrolled use of chemical pesticides, and herbicides, to cope with the rising crop demands of an ever-growing human population [ 1 , 2 ]. As a consequence of the massive use of agrochemicals, harmful effects such as environmental pollution, human health threats, insect resistance to pesticides, parasitoids, and pollinators loss occurred [ 3 , 4 , 5 ].…”

Sporulation efficiency and spore quality in a human intestinal isolate of Bacillus cereus

“…The experiment was performed either in LB medium (10 g Bacto-Tryptone, 5g Bacto-yeast extract, 10g NaCl, pH 7.0), or in S7 minimal medium (50 mM morpholine-propane-sulfonic acid (MOPS) (adjusted to pH 7.0 with KOH), 10 mM (NH 4 ) 2 SO 4 , 5 mM potassium phosphate (pH 7.0), 2 mM MgCl 2 , 0.9 mM CaCl 2 , 50 μM MnCl 2 , 5 μM FeCl 3 , 10 μM ZnCl 2 , 2 μM thiamine hydrochloride, 20 mM sodium glutamate, 1% glucose, 0.1 mg/mL phenylalanine, and 0.1 mg/mL tryptophan) or in DSM, for 48 h without shaking, at 25 and 42°C. Then, biofilm production was assessed by crystal violet assay as previously described in Petrillo et al, 2021. Data were normalized by total growth estimated by OD 590nm , and the experiment was performed in triplicate.…”