Journal of Basic Microbiology

A search for lipases was conducted in the radiophile of Deinococcus radiodurans R1. Four putative lipase genes, encoding DR0334, DR2078, DR1485, and DR2522, were cloned and expressed in Escherichia coli. The recombinant enzymes were subsequently purified and characterized. The results showed DR0334 and DR2078 had the ability to hydrolyze long‐chain length p‐nitrophenyl esters (C12–C16), while DR1485 and DR2522 hydrolyzed short‐ and medium‐chain length p‐nitrophenyl esters (C2–C10). DR0334, DR1485, DR2078, and DR2522 showed optimum pH at 8.5, and optimum temperature at 40, 50, 60, and 60 °C, respectively. DR0334 almost lost its whole activity after 60 min pretreatment at 60 °C, while DR1485, DR2078, and DR2522 retained more than 70% of their original activities after 6 h incubation at 80 °C. The activities of DR2078, DR1485, and DR2522 were enhanced by Mg²⁺, Ba²⁺, and Mn²⁺, but strongly inhibited by EDTA. Nevertheless, DR2078, DR1485, and DR2522 showed moderate stability in organic solvents and detergents. Phylogenetic analysis revealed that DR0334 and DR2078, respectively belong to family IV and family IX, while each of DR1485 and DR2522 forms a new separate branch. The unique properties of DR2078, DR1485, and DR2522, thermostability and organic solvent tolerance, make them useful in industrial applications.

Iron is one of the major limiting factors and essential nutrients of microbial life. Since in nature it is not readily available in the preferred form, microorganisms produce small high affinity chelating molecules called siderophores for its acquisition. Microorganisms produce a wide variety of siderophores controlled at the molecular level by different genes to accumulate, mobilize and transport iron for metabolism. Siderophores also play a critical role in the expression of virulence and development of biofilms by different microbes. Apart from maintaining microbial life, siderophores can be harnessed for the sustainability of human, animals and plants. With the advent of modern molecular tools, a major breakthrough is taking place in the understanding of the multifaceted role of siderophores in nature. This mini review is intended to provide a general overview on siderophore along with its role and applications.

A total of 216 killer yeasts Saccharomyces cerevisiae, isolated from wine, were evaluated in controlling Colletotrichum gloeosporioides, a pre‐harvest anthracnose agent of grape. Three of these yeast isolates were tested positive for antagonizing C. gloeosporioides and were further evaluated for their mechanisms as biological control agents (BCAs): production of antifungal compounds, production of hydrolytic enzymes, inhibition of C. gloeosporioides conidia germination, colonization on grape berry, and efficiency in controlling anthracnose of grape. The results showed that all three S. cerevisiae isolates produced antifungal compounds, inhibited C. gloeosporioides conidia germination and produced β‐1,3‐glucanase and chitinase. All isolates colonized grape berry in large quantities and controlled C. gloeosporioides when artificially inoculated on grape berry. Among the three isolates, application of isolate GA8 resulted in 69.7% of disease reductions for C. gloeosporioides on grape berry. The antagonistic isolates of S. cerevisiae could represent important BCAs of anthracnose of grape caused by C. gloeosporioides that are responsible for economic losses in viticulture.

Aspergillus nidulans produces sterigmatocystin, a secondary metabolite mycotoxin, for the protection of its reproductive structures. Previous studies on grazing behavior of fungivore arthropods, regulation of sexual development, and secondary metabolite biosynthesis have revealed the association of sterigmatocystin biosynthesis with sexual reproduction, but the spatial distribution of sterigmatocystin producing hyphae within the colony has never been investigated. In this work, we aimed to locate the site of sterigmatocystin production within the colony by employing a yCFP reporter system. We demonstrated that the stcO promoter is active only in vegetative hyphae that surround groups of hülle cells and the activity decreases and eventually ceases as the distance between the hypha and the hülle cells increases. This phenomenon indicates that the vegetative mycelium might consist of morphologically uniform, but functionally different hyphae.

A thermostable extracellular alkaline protease producing Bacillus amyloliquefaciens SP1 was isolated from apple rhizosphere having multifarious plant growth promoting activities. Strain SP1 was purified to 6.48‐fold using four‐step purification protocol and characterized in detail for its robustness and ecofriendly application in leather and detergent industries. Structural analysis revealed that the protease was monomeric and had a molecular weight of 43 kDa. It exhibited optimum activity at 60°C in alkaline environment (pH 8.0) and stable in the presence of surfactants and oxidizing agents. Enzyme was thermostable at 50°C and retained more than 70% activity after 30 min incubation. It has shown stain removal property and dehairing of goat skin without chemical assistance and hydrolyzing fibrous proteins. This protease showed Km of 0.125 mg ml⁻¹ and V_max of 12820 μg ml⁻¹ indicating its excellent affinity and catalytic role. Thermal inactivation of the pure enzyme followed first‐order kinetics. The half life of the pure enzyme at 50, 60, and 65°C was 77, 19.80, and 13.33 min, respectively. The activation energy was 37.19 KJ mol⁻¹. The results suggest that the B. amyloliquefaciens SP1 has a potential application in different industries.