Prospecting the plant growth–promoting activities of endophytic bacteria Cronobacter sp. YSD YN2 isolated from Cyperus esculentus L. var. sativus leaves

Plant growth-promoting and biocontrol traits of endophytic Bacillus licheniformis against soft rot causing Pythium myriotylum in ginger plant

Bacterial endophytes from plants harbor diverse metabolites that play major roles in biocontrol and improve plant growth. In this study, a total of 12 endophytic bacteria were isolated from the ginger rhizome. The strain K3 was highly effective in preventing mycelia growth of Pythium myriotylum (78.5 ± 1.5% inhibition) in dual culture. The cell-free extract (2.5%) of endophyte K3 inhibited 76.3 ± 4.8% mycelia growth, and 92.4 ± 4.2% inhibition was observed at a 5% sample concentration. The secondary metabolites produced by Bacillus licheniformis K3 showed maximum activity against Pseudomonas syringae (24 ± 1 mm zone of inhibition) and Xanthomonas campestris (28 ± 3 mm zone of inhibition). The strain K3 produced 28.3 ± 1.7 IU mL-1 protease, 28.3 ± 1.7 IU mL-1 cellulase, and 2.04 ± 0.13 IU mL-1 chitinase, respectively. The ginger rhizome treated with K3 in the greenhouse registered 53.8 ± 1.4% soft rot incidence, and the streptomycin-treated pot registered 78.3 ± 1.7% disease incidence. The selected endophyte K3 improved ascorbate peroxidase (1.37 ± 0.009 µmole ASC min-1 mg-1 protein), catalase (8.7 ± 0.28 µmole min-1 mg-1 protein), and phenylalanine ammonia-lyase (26.2 ± 0.99 Umg-1) in the greenhouse. In addition, K3 treatment in the field trial improved rhizome yield (730 ± 18.4 g) after 180 days (p < 0.01). The shoot length was 46 ± 8.3 cm in K3-treated plants, and it was about 31% higher than the control treatment (p < 0.01). The lytic enzyme-producing and growth-promoting endophyte is useful in sustainable crop production through the management of biotic stress.

Application of Atmospheric and Room-Temperature Plasma (ARTP) to Microbial Breeding

Atmospheric and room-temperature plasma (ARTP) is an efficient microbial mutagenesis method with broad application prospects. Compared to traditional methods, ARTP technology can more effectively induce DNA damage and generate stable mutant strains. It is characterized by its simplicity, cost-effectiveness, and avoidance of hazardous chemicals, presenting a vast potential for application. The ARTP technology is widely used in bacterial, fungal, and microalgal mutagenesis for increasing productivity and improving characteristics. In conclusion, ARTP technology holds significant promise in the field of microbial breeding. Through ARTP technology, we can create mutant strains with specific genetic traits and improved performance, thereby increasing yield, improving quality, and meeting market demands. The field of microbial breeding will witness further innovation and progress with continuous refinement and optimization of ARTP technology.

Microbiome differences in sugarcane and metabolically engineered oilcane accessions and their implications for bioenergy production

Oilcane is a metabolically engineered sugarcane (Saccharum spp. hybrid) that hyper-accumulates lipids in its vegetable biomass to provide an advanced feedstock for biodiesel production. The potential impact of hyper-accumulation of lipids in vegetable biomass on microbiomes and the consequences of altered microbiomes on plant growth and lipid accumulation have not been explored so far. Here, we explore differences in the microbiome structure of different oilcane accessions and non-modified sugarcane. 16S SSU rRNA and ITS rRNA amplicon sequencing were performed to compare the characteristics of the microbiome structure from different plant compartments (leaf, stem, root, rhizosphere, and bulk soil) of four greenhouse-grown oilcane accessions and non-modified sugarcane. Significant differences were only observed in the bacterial microbiomes. In leaf and stem microbiomes, more than 90% of the entire microbiome of non-modified sugarcane and oilcane was dominated by similar core taxa. Taxa associated with Proteobacteria led to differences in the non-modified sugarcane and oilcane microbiome structure. While differences were observed between multiple accessions, accession 1566 was notable in that it was consistently observed to differ in its microbial membership than other accessions and had the lowest abundance of taxa associated with plant-growth-promoting bacteria. Accession 1566 is also unique among oilcane accessions in that it has the highest constitutive expression of the WRI1 transgene. The WRI1 transcription factor is known to contribute to significant changes in the global gene expression profile, impacting plant fatty acid biosynthesis and photomorphogenesis. This study reveals for the first time that genetically modified oilcanes associate with distinct microbiomes. Our findings suggest potential relationships between core taxa, biomass yield, and TAG in oilcane accessions and support further research on the relationship between plant genotypes and their microbiomes.

Valorization as a biofertilizer of an agricultural residue leachate: Metagenomic characterization and growth promotion test by PGPB in the forage plant Medicago sativa (alfalfa)

The abuse of chemical fertilizers in intensive agriculture has turned out in the contamination of ground and the soil on which they are applied. Likewise, the generation, storage, and destruction of plant residues from the agri-food industry poses a threat to the environment and human health. The current situation of growing demand for food implies the urgent need to find sustainable alternatives to chemical fertilizers and the management of agricultural waste. Valorization of this plant residue to produce natural biofertilizers using microbiological treatments is presented as a sustainable alternative. The microbial activity allows the transformation into simple molecules that are easily absorbed by plants, as well as the stimulation of plant growth. This double direct and indirect action induced significant increases against the variables of germination, viability, and biomass (dry weight). To guarantee biosafety, it is necessary to use new bio-technological tools, such as metagenomics, which allow the taxonomic analysis of microbial communities, detecting the absence of pathogens. In the present paper, a physicochemical and metagenomic characterization of a fertilizer obtained from agricultural plant waste valorization is carried out. Likewise, fertigation treatments were tested to which the Plant Growth Promoting Bacteria (PGPB) Pseudomonas agronomica and Bacillus pretiosus were added, both independently and in consortium. Metagenomic analysis has identified taxa belonging to the kingdoms Bacteria and Archaea; 10 phyla, 25 families, 32 genera and 34 species, none of them previously described as pathogenic. A 1/512 dilution of the fertilizer increased the germination rate of Medicago sativa (alfalfa) by 16% at 144 h, compared to the treatment without fertilizer. Both the fertilizer and the addition of PGPB in a double direct and indirect action induced significant increases against the variables of germination, viability, and biomass (dry weight). Therefore, the use of an agricultural residue is proposed, which after the addition of two new species is transformed into a biofertilizer that significantly induces plant growth in Mendicago sativa plants.

Advances in characterization of probiotics and challenges in industrial application

An unbalanced diet and poor lifestyle are common reasons for numerous health complications in humans. Probiotics are known to provide substantial benefits to human health by producing several bioactive compounds, vitamins, short-chain fatty acids and short peptides. Diets that contain probiotics are limited to curd, yoghurt, kefir, kimchi, etc. However, exploring the identification of more potential probiotics and enhancing their commercial application to improve the nutritional quality would be a significant step to utilizing the maximum benefits. The complex evolution patterns among the probiotics are the hurdles in their characterization and adequate application in the industries and dairy products. This article has mainly discussed the molecular methods of characterization that are based on the analysis of ribosomal RNA, whole genome, and protein markers and profiles. It also has critically emphasized the emerging challenges in industrial applications of probiotics.