Assessment of variation in paddy microbial communities under different storage temperatures and relative humidity by Illumina sequencing analysis

Isolation and Characterization of Paenibacillus polymyxa B7 and Inhibition of Aspergillus tubingensis A1 by Its Antifungal Substances

Screening of Bacillus with antagonistic effects on paddy mold pathogens to provide strain resources for biological control of mold in Oryza sativa L. screening of Bacillus isolates antagonistic towards Aspergillus tubingensis from rhizosphere soil of healthy paddy; classification and identification of antagonistic strains by biological characteristics and 16S rDNA sequence analysis; transcriptome sequencing after RNA extraction from Bacillus-treated Aspergillus tubingensis; and extraction of inhibitory crude proteins of Bacillus by ammonium sulfate precipitation; inhibitory crude protein and Bacillus spp. were treated separately for A. tubingensis and observed by scanning electron microscopy (SEM). An antagonistic strain of Bacillus, named B7, was identified as Paenibacillus polymyxa by 16S rDNA identification and phylogenetic evolutionary tree comparison analysis. Analysis of the transcriptome results showed that genes related to secondary metabolite biosynthesis such as antifungal protein were significantly downregulated. SEM results showed that the mycelium of A. tubingensis underwent severe rupture after treatment with P. polymyxa and antifungal proteins, respectively. In addition, the sporocarp changed less after treatment with P. polymyxa, and the sporangium stalks had obvious folds. P. polymyxa B7 has a good antagonistic effect against A. tubingensis and has potential for biocontrol applications of paddy mold pathogens.

Deciphering the Microbiological Mechanisms Underlying the Impact of Different Storage Conditions on Rice Grain Quality

Different storage conditions can influence microbial community structure and metabolic functions, affecting rice grains' quality. However, the microbiological mechanisms by which different storage conditions affect the quality of rice grains are not yet well understood. This study monitored the quality (the content of starch, protein, etc.) and microbial community structure of rice grains stored under different storage conditions with nitrogen gas atmosphere (RA: normal temperature, horizontal ventilation, RB: normal temperature, vertical ventilation, RC: quasi-low temperature, horizontal ventilation). The results revealed that the rice grains stored under condition RB exhibited significantly lower quality compared to condition RA and RC. In addition, under this condition, the highest relative abundance of Aspergillus (16.0%) and Penicillium (0.4%) and the highest levels of aflatoxin A (3.77 ± 0.07 μg/kg) and ochratoxin B1 (3.19 ± 0.05 μg/kg) were detected, which suggested a higher risk of fungal toxin contamination. Finally, co-occurrence network analysis was performed, and the results revealed that butyl 1,2-benzenedicarboxylate was negatively correlated (p < 0.05) with Moesziomyces and Alternaria. These findings will contribute to the knowledge base of rice storage management and guide the development of effective control measures against undesirable microbial activities.

The Effects of Ventilation, Humidity, and Temperature on Bacterial Growth and Bacterial Genera Distribution

BACKGROUND

Bacteria are readily nourished in airtight environments with high humidity, such as storage cabinets, clothing closets, and corners, where ventilation is normally low and humidity is high.

OBJECTIVES

We characterized the role of humidity and ventilation in bacterial growth and genus distribution at different temperatures (26 °C and 34 °C).

METHODS

Fresh pork, which was used as the substrate for bacterial culture, was placed in storage cabinets. Bacterial growth and genera distribution on the surface of pork placed in a storage cabinet under different temperatures (26 °C and 34 °C); relative humidity levels (RH: 50%, 70%, 90%); and ventilation conditions (no ventilation and low, medium, and high levels of ventilation) were assessed by rDNA sequencing.

RESULTS

Increased ventilation and reduced humidity significantly decreased bacterial growth at 26 °C and 34 °C. The contribution of increased ventilation to the reduction in bacterial growth exceeded that of decreased humidity. Ventilation had the greatest effect on reducing bacterial growth compared to the unventilated conditions at 70% RH. At 34 °C, medium and high levels of ventilation were required to reduce bacterial growth. High temperatures greatly increased bacterial growth, but ventilation could reduce the degree of this increase.

Analysis of the Fungi Community Variation during Rice Storage through High Throughput Sequencing

Rice storage conditions include location, granary depth, storage time, temperature and atmosphere. The fungi community varies during storage, but how these communities change remains unexplored so far. This study collected rice samples from granaries in different horizontal and vertical directions and storage time over two years. High-throughput ITS (Internal Transcribed Spacer) sequencing analysis revealed that Ascomycota (73.81%), Basidiomycota (6.56%) and Mucoromycota (9.42%) were the main Eumycota present during rice storage. The main fungi communities were Aspergillus sp., Fusarium sp., Rhizopus sp., Gibberella sp., Tilletia sp. and Penicillium sp. The contribution of storage time, horizontal orientation and vertical depth effect on fungi community relative abundance were 17.18%, 5.98% and 0.11%, respectively. Aspergillus sp. was the predominant Eubacterium during this process. The horizontal A was mainly occupied by Paraconiothyrium sp. and the location S, had Clavispora sp. Both of these varied dramatically during storage. Furthermore, Aspergillus sp., as a main mycotoxin producer, was the dominant fungi at vertical L1. This study comprehensively analyzed fungi community variation in horizontal and vertical directions to elucidate fungi community variation on rice during storage and to find the detrimental fungi. Therefore, it is important to improve granary ventilation systems and to ensure a uniform atmosphere to control fungi growth.

Diversity Analysis of Bacterial and Function Prediction in Hurunge From Mongolia

With the continuous infiltration of industrialization and modern lifestyle into pastoral areas, the types and processing capacity of Hurunge are decreasing, and the beneficial microbial resources contained in it are gradually disappearing. The preservation and processing of Hurunge are very important for herdsmen to successfully produce high-quality koumiss in the second year. Therefore, in this study, 12 precious Hurunge samples collected from Bulgan Province, Ovorkhangay Province, Arkhangay Province, and Tov Province of Mongolia were sequenced based on the V3-V4 region of the 16S rRNA gene, and the bacterial diversity and function were predicted and analyzed. There were significant differences in the species and abundance of bacteria in Hurunge from different regions and different production methods (p < 0.05). Compared with the traditional fermentation methods, the OTU level of Hurunge fermented in the capsule was low, the Acetobacter content was high and the bacterial diversity was low. Firmicutes and Lactobacillus were the dominant phylum and genus of 12 samples, respectively. The sample QHA contained Komagataeibacter with the potential ability to produce bacterial nanocellulose, and the abundance of Lactococcus in the Tov Province (Z) was significantly higher than that in the other three regions. Functional prediction analysis showed that genes related to the metabolism of bacterial growth and reproduction, especially carbohydrate and amino acid metabolism, played a dominant role in microorganisms. In summary, it is of great significance to further explore the bacterial diversity of Hurunge for the future development and research of beneficial microbial resources, promotion, and protection of the traditional ethnic dairy products.

Compared analysis of microbial diversity in donkey milk from Xinjiang and Shandong of China through High-throughput sequencing

Donkey milk has received increasing attention from consumers and dairy industry because of its nutritional value, health benefits, and proximity to human milk. Microbial diversity in donkey milk has a great impact on its quality and safety, however, microbiota in donkey milk from the major donkey-breeding regions of China have not been well documented. In this study, bacterial communities in donkey milk from Yopurga County in Western China (XJ), and Dong'e County in Eastern China (SD) were determined using high-throughput sequencing. Major phyla identified in the two donkey milk groups consistently included Acinetobacter, Proteobacteria, Firmicutes, and Bacteroidetes but with very different abundance for each phylum. Prevelence of genera was found to be diverse between the two groups, with Macrococcus and Acinetobacter dominating in the XJ samples while Streptococcus, Pseudoclavibacter, and Pseudomonas being the most abundant ones in the XJ samples. Alpha diversity analysis showed that there was significant difference in richness between the two sample groups but no difference in bacterial community diversity or coverage. The presence of possible harmful bacteria and lactic acid bacteria in donkey milk in this study provides the microbial profiles of pathogens and spoilage bacteria that need to be controlled and proposes possible utilization of beneficial microbial resources for the future.