Peroxidase-producing actinobacteria from Algerian environments and insights from the genome sequence of peroxidase-producing Streptomyces sp. S19 / Actinobacteria productora de peroxidasa de ambientes argelinos y perspectivas de la secuencia genómica de Streptomyces sp. S19

Unique environments often serve as a source of novel microorganisms with novel chemistries. In this study, telluric samples collected from different regions of Algeria were processed for the isolation of novel peroxidase-producing actinobacterial strains. An agar-based screening identified 45 isolates with the ability to produce peroxidase. The 16S rRNA gene sequencing showed that most of the strains belong to the genus Streptomyces. Optimization of cultivation conditions was performed for the top five peroxidase-producing strains. Apart from strain 36 (optimal growth temperature of 30 °C) and strain 45 (optimal medium pH of 6.0), the strains exhibited optimal peroxidase production when cultivated for 5 days at 37 °C and in a medium at pH 7.0. Extracellular peroxidase production was induced by ferulic acid in three of the five strains, while the presence of canola lignocellulosic waste (CLW) induced peroxidase production in all strains. Strain 19 (S19) was selected for further optimization and the extracellular peroxidase purified using acid and acetone precipitation, followed by size exclusion chromatography. The purified fraction showed a single band on the polyacrylamide gel with an estimated molecular weight of 21.45 kDa. Genome analysis confirmed the assignment of S19 to the genus Streptomyces, the presence of genes encoding for peroxidases, and the presence of genes encoding for carbohydrate-active enzymes. The presence of biosynthetic gene clusters potentially encoding for biosurfactants further highlighted the great biotechnological potential of the strain.(AU)

Transcriptomics of the Rooibos (Aspalathus linearis) Species Complex.

Rooibos (Aspalathus linearis), widely known as a herbal tea, is endemic to the Cape Floristic Region of South Africa (SA). It produces a wide range of phenolic compounds that have been associated with diverse health promoting properties of the plant. The species comprises several growth forms that differ in their morphology and biochemical composition, only one of which is cultivated and used commercially. Here, we established methodologies for non-invasive transcriptome research of wild-growing South African plant species, including (1) harvesting and transport of plant material suitable for RNA sequencing; (2) inexpensive, high-throughput biochemical sample screening; (3) extraction of high-quality RNA from recalcitrant, polysaccharide- and polyphenol rich plant material; and (4) biocomputational analysis of Illumina sequencing data, together with the evaluation of programs for transcriptome assembly (Trinity, IDBA-Trans, SOAPdenovo-Trans, CLC), protein prediction, as well as functional and taxonomic transcript annotation. In the process, we established a biochemically characterized sample pool from 44 distinct rooibos ecotypes (1-5 harvests) and generated four in-depth annotated transcriptomes (each comprising on average ≈86,000 transcripts) from rooibos plants that represent distinct growth forms and differ in their biochemical profiles. These resources will serve future rooibos research and plant breeding endeavours.

Secretory expression of recombinant small laccase from Streptomyces coelicolor A3(2) in Pichia pastoris.

This work reports for the first time the secretory expression of the small laccase (SLAC) from Streptomyces coelicolor A3(2) in Pichia pastoris. Using an AOX1 promoter and α factor as a secretion signal, the recombinant P. pastoris harbouring the laccase gene (rSLAC) produced high titres of extracellular laccase (500 ±â€¯10 U/l), which were further increased seven fold by pre-incubation at 80 °C for 30 min. The enzyme (∼38 kDa) had an optimum activity at 80 °C, but optimum pH varied with substrate used. Km values for ABTS, SGZ and 2,6-DMP were 142.85 µM, 10 µM and 54.55 µM and the corresponding kcat values were 60.6 s-1, 25.36 s-1 and 27.84 s-1, respectively. The t1/2 values of the rSLAC at 60 °C, 70 °C, 80 °C were 60 h, 32 h and 10 h, respectively. The enzyme deactivation energy (Ed) was 117.275 kJ/mol while ΔG, ΔH and ΔS for thermal inactivation of the rSLAC were all positive. The rSLAC decolourised more than 90% of Brilliant Blue G and Trypan Blue dye in 6 h without the addition of a mediator. High titres of SLAC expressed in P. pastoris enhance its potential for various industrial applications.

Enhanced Antimicrobial and Anticancer Activity of Silver and Gold Nanoparticles Synthesised Using Sargassum incisifolium Aqueous Extracts.

A detailed, methodical approach was used to synthesise silver and gold nanoparticles using two differently prepared aqueous extracts of the brown algae Sargassum incisifolium. The efficiency of the extracts in producing nanoparticles were compared to commercially available brown algal fucoidans, a major constituent of brown algal aqueous extracts. The nanoparticles were characterised using TEM, XRD and UV/Vis spectroscopy and zeta potential measurements. The rate of nanoparticle formation was assessed using UV/Vis spectroscopy and related to the size, shape and morphology of the nanoparticles as revealed by TEM. The antioxidant, reducing power and total polyphenolic contents of the aqueous extracts and fucoidans were determined, revealing that the aqueous extracts with the highest contents produced smaller, spherical, more monodisperse nanoparticles at a faster rate. The nanoparticles were assessed against two gram-negative bacteria, two gram-positive bacteria and one yeast strain. In contrast to the literature, the silver nanoparticles produced using the aqueous extracts were particularly toxic to Gram-negative bacteria, while the gold nanoparticles lacked activity. The cytotoxic activity of the nanoparticles was also evaluated against cancerous (HT-29, MCF-7) and non-cancerous (MCF-12a) cell lines. The silver nanoparticles displayed selectivity, since the MCF-12a cell line was found to be resistant to the nanoparticles, while the cancerous HT-29 cell line was found to be sensitive (10% viability). The gold nanoparticles displayed negligible toxicity.