ABSTRACT
Antimicrobial peptides have the potential to be used in a range of applications, including as an alternative to conventional antibiotics for the treatment of bacterial infections of humans and animals. Therefore, there is interest in identifying novel bacteriocins which have desirable physico-chemical properties or antimicrobial activities. Paenibacillus polymyxa #23, isolated from a marine sponge, has wide spectrum antimicrobial activity against Gram-negative and Gram-positive bacteria. To explore the basis of this antimicrobial activity, the complete genome sequence of the strain was examined. Multiple genes predicted to encode antimicrobial peptides were identified. One gene was predicted to encode a novel sactipeptide bacteriocin, named SacP23. To confirm that SacP23 does have antimicrobial activity and to explore the antimicrobial spectrum of the peptide it was heterologously expressed in Bacillus subtilis. A cluster of eight genes, encoding a full complement of accessory genes as well as the structural gene expressed from the native promoter, was cloned into B. subtilis BS54A. The recombinant strain displayed antimicrobial activity against several Gram-positive bacteria, including multi-drug resistant Staphylococcus aureus. Heterologous expression of a whole gene cluster offers a powerful way to interrogate and resolve the various antimicrobial activities expressed by native strains that encode multiple compounds of interest.
ABSTRACT
k-Oligocarrageenan (OC) is an effective biostimulator and a protector against disease infections for plants. However, the effect of OC molecular weight (MW) on plant growth is not fully understood. In this work, OCs with three different MWs (42, 17 and 4 kDa) was prepared by varying the degradation reaction time using ascorbic acid as a reagent. The product structure was confirmed by Fourier-transform infrared spectroscopy (FTIR) data. The growth promotion for maize (Zea mays L.) plants was investigated by foliar spray application of the prepared OCs. Field trials were carried out in two years, 2018 and 2019. The results showed that among treatments, OC with 4 kDa exhibited the best performance in both crop growth and grain yield parameters which indicated increases compared to the control in plant height (6.9-19.9%), length of ears (12.2%), diameter of ears (9.1%), fresh grain weight (17.8%), dry grain weight (20.0%) and grain yield (21.3%). Moreover, low MW OC augmented NP uptake in the plant growth while no effect on K uptake was observed. Therefore, OC with low MWs is potentially promising to apply as a promoter to enhance yield of crops.
