Search Results (5)

Some Vibrio parahaemolyticus strains cause translucent post-larvae disease (Vp_TPD), leading to significant economic losses in shrimp farming. We aimed to identify whether a mixture of natural antimicrobials, AuraAqua (Aq), can protect white-leg shrimp (Penaeus vannamei) against the lethal effects of Vp_TPD and to understand its biological mode of action. Herein, we demonstrate that Aq, an antimicrobial mixture composed of a blend of organic acids, citrus, and olive extracts, suppressed Vp_TPD virulence at sub-inhibitory concentrations and conferred robust protection to shrimp. The minimum inhibitory and bactericidal concentrations against the Vp_TPD isolate were at 0.05% and 0.2%, respectively. At 0.05–0.1%, Aq reduced bacterial growth and downregulated six major virulence genes (vhvp-1, vhvp-2, vhvp-3, pirA_Vp, pirB_Vp, pirAB_Vp), while leaving metabolic ldh expression unaltered. Parallel in vitro assays revealed diminished adhesion of Vp_TPD to primary shrimp gut and hepatopancreas epithelial cells and a ≈50% reduction in infection-induced extracellular H₂O₂, indicating an antioxidant effect. The treatment also triggered a time-dependent surge in extracellular alkaline phosphatase (ALP) activity, consistent with membrane permeabilization. In vivo, a challenge of post-larvae with 10⁴ CFU/mL Vp_TPD resulted in 91% mortality after 45 h; co-treatment with 0.1% and 0.2% Aq reduced mortality to ≈12% and ≈6%, respectively, while 1% Aq achieved ≈98% survival. The clinical protection test confirmed that 0.1% Aq preserved high survival across four pathogen inocula (10¹–10⁴ CFU/mL). Conclusively, Aq destabilized the pathogen and therefore transcriptionally silenced multiple virulence determinants, translating into significant in-pond protection for controlling Vp_TPD for shrimp aquaculture. Full article

Anaerobic digestion (AD) is a well-established technology for the sustainable conversion of agricultural organic by-products and waste into bioenergy. Temperature is crucial for optimizing methane production through inocula preservation and reactor start-up in AD. The preservation of inocula induced by temperature has rarely been assessed from an engineering perspective. There has also been limited exploration of the influence of high-to-moderate temperature transition on the initiation of AD. This study employed continuous mesophilic AD reactors with potential engineering applications to conduct revival tests. These tests evaluated the methane production activity of sludge stored at different temperatures and investigated the impact of high-temperature initiation on mesophilic AD. Additionally, we elucidated the correlation between these assessments and microbial diversity as well as composition. The results indicated that bacterial diversity was higher in the inoculum stored at 35 °C compared to 15 °C, ensuring a stable start-up operation of the mesophilic AD. The richness of the bacteria and diversity of the archaea remained stable during the transition from high to mesophilic temperatures. This was conducive to enhancing methanogenic activity of mesophilic AD initiated at 55 °C. The continuously operated AD system showed significant differences in microbial composition compared to its inoculum. Increased abundance of Coriobacteriaceae and Prevotellaceae led to propionate and butyrate accumulation, respectively, reducing AD operational capacity. Methanogenic archaea were less diverse in AD initiated with low-temperature preserved inoculum compared to that with a medium temperature. Streptococcaceae induced by high temperarure could promote AD stability. Hydrogenotrophic methanogens had a competitive advantage in mesophilic AD due to their prior exposure to high-temperature initiation, possibly influenced by Thermotogaceae. Full article

Future manned space travel will require efficient recycling of nutrients from organic waste back into food production. Microbial systems are a low-energy, efficient means of nutrient recycling, but their use in a life support system requires predictability and reproducibility in community formation and reactor performance. To assess the reproducibility of microbial community formation in fixed-film reactors, we inoculated replicate anaerobic reactors from two methanogenic inocula: a lab-scale fixed-film, plug-flow anaerobic reactor and an acidic transitional fen. Reactors were operated under identical conditions, and we assessed reactor performance and used 16s rDNA amplicon sequencing to determine microbial community formation. Reactor microbial communities were dominated by similar groups, but differences in community membership persisted in reactors inoculated from different sources. Reactor performance overlapped, suggesting a convergence of both reactor communities and organic matter mineralization. The results of this study suggest an optimized microbial community could be preserved and used to start new, or restart failed, anaerobic reactors in a life support system with predictable reactor performance. Full article

Brassica yellows virus (BrYV) is a tentative species of the genus Polerovirus, which occurs widely, and mostly damages Brassicaceae plants in East Asia. Because BrYV cannot be transmitted mechanically, an insect-based transmission method is required for further virus research. Here, a reliable and unrestricted method is described, in which non-viruliferous aphids (Myzus persicae) acquired BrYV from transgenic Arabidopsis thaliana, harboring the full-length viral genome germinated from seeds and its frozen leaves. The aphids then transmitted the virus to healthy plants. There was no significant difference in acquisition rates between fresh and frozen infected leaves, although the transmission rate from frozen infected leaves was lower compared to fresh infected leaves. This simple novel method may be used to preserve viral inocula, evaluate host varietal resistance to BrYV, and investigate interactions among BrYV, aphids, and hosts. Full article

This work reports on the antimicrobial activity of an ethyl acetate extract of neem (Azadirachta indica) cake (NCE) against bacteria affecting the quality of retail fresh meat in a broth model meat system. NCE (100 µg) was also tested by the agar disc diffusion method. It inhibited the growth of all tested microorganisms. The NCE growth inhibition zone (IZ) ranged 11.33–22.67 mm while the ciprofloxacin (10 µg) IZ ranged from 23.41–32.67 mm. There was no significant difference (p ≤ 0.05) between the antimicrobial activity of NCE and ciprofloxacin vs. C. jejuni and Leuconostoc spp. The NCE antibacterial activity was moreover determined at lower concentrations (1:10–1:100,000) in micro-assays. The percent growth reduction ranged from 61 ± 2.08–92 ± 3.21. The higher bacterial growth reduction was obtained at 10 µg concentration of NCE. Species-specific PCR and multiplex PCR with the DNA dye propidium monoazide were used to directly detect viable bacterial cells from experimentally contaminated meat samples. The numbers of bacterial cells never significantly (p ≤ 0.05) exceeded the inocula concentration used to experimentally contaminate the NCE treated meat. This report represents a screening methodology to evaluate the antimicrobial capability of a herbal extract to preserve meat. Full article