Streptomyces nucleases

Characterization of 5'-nucleotidases secreted from Streptomyces

To study the ability of Streptomyces to utilize environmental nucleotides, we screened for strains exhibiting extracellular 5'-inosine monophosphate (IMP)-dephosphorylating activity in our collection of soil isolates and obtained two producers: NE5-10 and Y2F8-2. The enzyme responsible for the activity was purified from the culture supernatant of each strain, and its mass spectral data were used to identify the coding sequence. The gene was successfully identified in the whole genome sequence of each strain; it was located in a conserved gene cluster of phosphate-related functions and encoded an approximately 600-amino acid long protein containing an N-terminal secretion signal. The mature part of the protein exhibited similarity to a known bacterial 5'-nucleotidase. The locus of the 5'-nucleotidase gene contained genes encoding proteins involved in phosphate utilization. The conserved gene arrangement of the locus in various Streptomyces genomes suggested the genetic region to be involved in phosphate-scavenging in this group of bacteria. Phylogenetic analysis demonstrated that the isolated Streptomyces enzymes represent an uncharacterized group of bacterial 5'-nucleotidases. Enzymatic characterization of the two Streptomyces enzymes demonstrated that both enzymes exhibited 5'-nucleotidase activity but differed in terms of optimal temperature and pH, dependence on divalent cations, and substrate specificity. The Km and Vmax values of the 5'-IMP-dephosphorylating activity were 0.239 mM and 9.47 U/mg, respectively, for NE5-10 and 0.221 mM and 38.17 U/mg, respectively, for Y2F8-2. Enzyme activity in the culture broth of the two Streptomyces producers occurred in a phosphate-limitation-dependent manner, supporting their involvement in the acquisition of phosphorus. KEY POINTS: • We purified and characterized nucleotidases from two Streptomyces. • Two nucleotidases were presumed to be involved in phosphate acquisition. • It showed diversity in phosphate acquisition among microorganisms.

Pathogen-Derived Nucleases: An Effective Weapon for Escaping Extracellular Traps

Since the 2004 publication of the first study describing extracellular traps (ETs) from human neutrophils, several reports have shown the presence of ETs in a variety of different animals and plants. ETs perform two important functions of immobilizing and killing invading microbes and are considered a novel part of the phagocytosis-independent, innate immune extracellular defense system. However, several pathogens can release nucleases that degrade the DNA backbone of ETs, reducing their effectiveness and resulting in increased pathogenicity. In this review, we examined the relevant literature and summarized the results on bacterial and fungal pathogens and parasites that produce nucleases to evade the ET-mediated host antimicrobial mechanism.

High quality draft genome sequence of Streptomyces sp. strain AW19M42 isolated from a sea squirt in Northern Norway

Here we report the 8 Mb high quality draft genome of Streptomyces sp. strain AW19M42, together with specific properties of the organism and the generation, annotation and analysis of its genome sequence. The genome encodes 7,727 putative open reading frames, of which 6,400 could be assigned with COG categories. Also, 62 tRNA genes and 8 rRNA operons were identified. The genome harbors several gene clusters involved in the production of secondary metabolites. Functional screening of the isolate was positive for several enzymatic activities, and some candidate genes coding for those activities are listed in this report. We find that this isolate shows biotechnological potential and is an interesting target for bioprospecting.

Increased alkalotolerant and thermostable ribonuclease (RNase) production from alkaliphilic Streptomyces sp. M49-1 by optimizing the growth conditions using response surface methodology

Total of 171 alkaliphilic actinomycetes were evaluated for extracellular RNase production and Streptomyces sp. M49-1 was selected for further experiments. Fermentation optimization for RNase production was implemented in two steps using response surface methodology with central composite design. In the first step, the effect of independent fermentation variables including temperature, initial pH and process time were investigated. After identification of carbon and nitrogen sources affecting the production by one variable at a time method, concentrations of glucose and yeast extract and also inoculum size were chosen for the second central composite design. A maximum RNase activity was obtained under optimal conditions of 4.14 % glucose concentration, 4.63 % yeast extract concentration, 6.7 × 10⁶ spores as inoculum size for 50 ml medium, 42.9 °C, 91.2 h process time and medium initial pH 9.0. Optimum activity of the enzyme is achieved at pH 11 and temperature 60 °C. The enzyme is highly stable at pH range 9.0-12.0 and at 90 °C after 2 h. Statistical optimization experiments provide 2.25 fold increases in the activity of alkalotolerant and thermostable RNase and shortened the fermentation time compared to that of unoptimized condition. The members of Streptomyces can be promising qualified RNase producer for pharmaceutical industries.