Bacillus subtilis, an ideal probiotic bacterium to shrimp and fish aquaculture that increase feed digestibility, prevent microbial diseases, and avoid water pollution

Isolation of a new Streptomyces virginiae W18 against fish pathogens and its effect on disease resistance mechanism of Carassius auratus

The Streptomyces virginiae strain W18 was screened from soil, which exhibited broad-spectrum antibacterial activity against fish pathogens. Safety assays showed that strain W18 had no toxicity to fish. Additionally, strain W18 promoted the growth performance of Carassius auratus after feeding in feed mixed with bacteria for one month. Moreover, the activities of AKP, ACP, and SOD in the serum of C. auratus were significantly increased, while the activity of LZM did not greatly change. To detect the expression levels of the genes related to immune factors in the livers, kidneys, and spleens of C. auratus, qRT-PCR was performed. The expression levels of KEAP1, IL-8, TNF-α, IL-β, and C3 were upregulated in all three organs compared to the control, but LZM expression was downregulated in the kidney. The challenge experiment illustrated that the probability of infection with Aeromonas veronii was reduced by 60% and 40% when C. auratus was fed with two different doses of strain W18 in advance. The whole genome of strain W18 was sequenced, and the gene clusters of secondary metabolites in strain W18 were analyzed by AntiSMASH. The results showed that strain W18 contained a total of 26 gene clusters, and functional annotation analysis was conducted by using the non-coding databases COG and KEGG. All of the above results indicated that the use of strain W18 as a feed additive could enhance the resistance of C. auratus toward pathogenic bacteria and disease. In conclusion, an antagonistic strain (W18) against fish pathogenic bacteria was obtained in this study, which is of great significance for finding new treatment methods for bacterial diseases in the aquaculture industry.

Anti-Inflammatory and Antimicrobial Volatile Oils: Fennel and Cumin Inhibit Neutrophilic Inflammation via Regulating Calcium and MAPKs

Neutrophilic inflammatory diseases, such as chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome (ARDS), or psoriasis, exert a huge burden on the global health system due to the lack of safe and effective treatments. Volatile oils from terrestrial plants showed impressive therapeutic effects against disorders of the skin, digestive system, lungs, liver, metabolism, and nervous system. However, their effect on the immune system and neutrophil function is still elusive. Fennel, cumin, marjoram, lavender, caraway, and anise are the common nutraceuticals that are widely used in the Mediterranean diet. The volatile oils of these herbs were screened for various biological activities, including anti-inflammatory, anti-allergic, antimicrobial, and antiviral effects. Several oils showed anti-inflammatory and antimicrobial potential. Fennel (Foeniculum vulgare) and cumin (Cuminum cyminum) fruits' volatile oils significantly suppressed the activation of human neutrophils, including respiratory burst and the degranulation induced by formyl peptide receptor agonists fMLF/CB and MMK1 in the human neutrophils (IC₅₀, 3.8–17.2 µg/ml). The cytotoxic effect and free-radical scavenging effects (ABTS, DPPH) of these oils did not account for the observed effects. Both fennel and cumin volatile oils significantly shortened calcium influx recovery time and inhibited phosphorylation of mitogen-activated protein kinases (p38, JNK, and ERK) expression. The gas chromatography–mass spectrometry analysis of these oils revealed the presence of estragole and cuminaldehyde as the major components of fennel and cumin volatile oils, respectively. Our findings suggested that cumin and fennel, common in the Mediterranean diet, hold the potential to be applied for the treatment of neutrophilic inflammatory diseases.

Dietary supplementation of Bacillus velezensis B8 enhances immune response and resistance against Aeromonas veronii in grass carp

The heavy use of prophylactic antibiotics in aquaculture leads to elevated antibiotic residues, posing a huge hidden danger in aquaculture products and other natural aquatic environments. Therefore, this study aims to isolate probiotics that can replace antibiotics from the gut of grass carp for disease control. Bacillus velezensis B8 was isolated from the gut of grass carp and showed broad-spectrum antimicrobial activity against several fish pathogenic bacteria, including Aeromonas hydrophilis, Aeromonas veronii, Vibrio parahaemolyticus, Escherichia coli, Edwardsiella tarda and Vibrio mimicus. The safety evaluation showed that the strain B8 was non-toxic to grass carp, had no hemolytic activity, and was sensitive to most antibiotics. In vitro study indicated that strain B8 was viable at pH 2-7, had weak tolerance to 0.1% (w/v) bile salt, and could grow at 10°C-40 °C. The grass carps were fed with diets containing 0 (control), 10⁷, and 10⁹ cfu/g of strain B8 for 4 weeks. Various immune parameters were measured at 1, 2, 3, and 4 weeks of post-feeding. The results of non-specific immunoassay showed that diets supplemented with B8 significantly increased alkaline phosphatase (AKP) and superoxide dismutase (SOD) activity in serum samples (p < 0.05). The expression levels of immune-related genes in the kidney and spleen of grass carp were measured. Among them, the expression levels of IgM and TNF-α both in spleen and kidney were significantly increased after 3 and 4 weeks of post-feeding (p < 0.05). The expression of IgD and MHCI in kidney was significantly upregulated in high-dose groups after 2 and 3 weeks of feeding, respectively (p < 0.05). In addition, after 7 days of challenging with A. veronii, the high-dose group and low-dose group had 48% and 53% survival compared to 25% survival for the control group. These results suggest that B. velezensis B8 has the potential to be developed into a microecological preparation for the alternatives of antibiotics in aquaculture.

Usefulness of a 3D-printing air sampler for capturing live airborne bacteria and exploring the environmental factors that can influence bacterial dynamics

We created a handmade 3D-printed air sampler to effectively collect live airborne bacteria, and determined which environmental factors influenced the bacteria. Bacterial colony forming units (CFUs) in the air samples (n=37) were monitored by recording the environmental changes occurring over time, then determining the presence/absence of correlations among such changes. The bacterial CFUs changed sharply and were significantly correlated with the DNA concentrations, indicating that the captured bacteria made up most of the airborne bacteria. Spearman's rank correlation analysis revealed significant correlations between the bacterial CFU values and some environmental factors (humidity, wind speed, insolation, and 24-h rainfall). Similarly the significant associations of CFU with humidity and wind speed were also found by multiple regression analysis with box-cox transformation. Among our panel of airborne bacteria (952 strains), 70 strains were identified as soil-derived Bacillus via the production of Escherichia coli- and Staphylococcus aureus-growth inhibiting antibiotics and by 16S rDNA typing. Soil-derived protozoa were also isolated from the air samples. We conclude that the airborne bacteria mainly derived from soil can alter in number according to environmental changes. Our sampler, which was created by easy-to-customize 3D printing, is a useful device for understanding the dynamics of live airborne bacteria.

Low concentrations of imidacloprid exposure induced gut toxicity in adult zebrafish (Danio rerio)

Neonicotinoid insecticide imidacloprid (IMI) is widely used in agriculture, and its repeated application may result in environmental pollution. Recently, the toxicity of IMI to non-target animals has received increasing attention. In the current study, adult zebrafish were exposed to low concentrations of IMI (100 and 1000 μg/L) for 21 days. The results showed that IMI exposure induced intestinal histological injury and oxidative stress in the gut of zebrafish, and the levels of superoxide dismutase (SOD), catalase (CAT) were noticeably increased. Furthermore, IMI exposure also resulted in higher intestinal LPS levels and significant increases in the expression of inflammatory factors. Simultaneously, IMI exposure also slightly induced gut microbiota dysbiosis and specific bacteria alterations. These findings indicated that low concentrations of IMI could induce gut toxicity in adult zebrafish, which could provide new insights into the potential risks of IMI to aquatic animals.

Feed intake improvement, gut microbiota modulation and pathogens control by using Bacillus species in shrimp aquaculture

Aquaculture is one of the fastest-growing economic activities worldwide; shrimp production by aquaculture is around 70% or more of the total consumed. The development of this activity is inducing great benefits in the production of food and jobs; however, shrimp aquaculture is also generating; (1) ecological imbalance by pelagic species overexploitation to produce fish ingredients, (2) bays contamination by inappropriate waste management and (3) pathogens proliferation by antibiotics abuse. In this sense, a significant number of regulations and legal restrictions have been imposed; thus, aquaculture is no longer considered a profitable activity. Therefore, significant and innovative technologies need to be applied to ensure the sustainability and profitability of this activity. In this sense, probiotic bacteria are being used in aquaculture to improve feed intake, modulate gut microbiota and control pathogen proliferation. This work summarizes the results from researchers who worked extensively to show how probiotic bacteria can improve shrimp aquaculture development.

Bacillus subtilis Inhibits Viral Hemorrhagic Septicemia Virus Infection in Olive Flounder (Paralichthys olivaceus) Intestinal Epithelial Cells

Viral hemorrhagic septicemia virus (VHSV) is a highly pathogenic virus that infects a wide range of host fish species causing high economic losses in aquaculture. Epithelial cells in mucosal organs are target sites for VHSV entry into fish. To protect fish against VHSV infection, there is a need to develop antiviral compounds able to prevent establishment of infection at portals of virus entry into fish. Bacillus subtilis is a probiotic with excellent antiviral properties, of which one of its secretions, surfactin, has been shown to inhibit viral infections in mammals. Herein, we demonstrate its ability to prevent VHSV infection in olive flounder (Paralichthys olivaceus) intestinal epithelial cells (IECs) and infection in internal organs. Our findings show inhibition of VHSV infection in IECs by B. subtilis and surfactin. In addition, our findings showed inhibition of VHSV in Epithelioma Papulosum Cyprini (EPC) cells inoculated with intestinal homogenates from the fish pretreated with B. subtilis by oral exposure, while the untreated fish had cytopathic effects (CPE) caused by VHSV infection in the intestines at 48 h after the VHSV challenge. At 96 h post-challenge, samples from the untreated fish had CPE from head kidney and spleen homogenates and no CPE were observed in the intestinal homogenates, while the B. subtilis-pretreated fish had no CPE in all organs. These findings demonstrate that inhibition of VHSV infection at portals of virus entry in the intestines culminated in prevention of infection in internal organs. In summary, our results show that B. subtilis has the potential to prevent VHSV infection in fish and that its use as a probiotic in aquaculture has the potential to serve as an antiviral therapeutic agent against different viral infections.

Effects of Bacillus amyloliquefaciens and Bacillus pumilus on Rumen and Intestine Morphology and Microbiota in Weanling Jintang Black Goat

The importance of Bacillus as feed additives in animals' production is well recognized. Bacillus amyloliquefaciens and Bacillus pumilus are involved in promoting animal growth performance and immunological indicators. However, their precise roles in the modulation of microbiota and immune response in goat rumen and intestines have not been investigated. The aim of the current work was to evaluate the impacts of Bacillus amyloliquefaciens fsznc-06 and Bacillus pumilus fsznc-09 in the development of rumen and small intestinal and microbial communities in rumen and caecum of weanling Jintang black goats. Morphological alterations of rumen and small intestine (duodenum, jejunum, and ileum) were evaluated by histochemical staining, and ruminal contents and cecal feces were analyzed by 16S rRNA sequencing in an Illumina NovaSeq platform. Morphological analysis showed that feeding weanling goats with Bacillus amyloliquefaciens fsznc-06 or Bacillus pumilus fsznc-09 enhanced ruminal papilla and small intestinal villus growth. In addition, 16S rRNA sequencing analysis indicated that microbial richness and diversity (Shannon, Simpson, Chao1, and ACE) and the relative richness of multiple or potential beneficial bacteria were higher in weaned black goats fed on Bacillus amyloliquefaciens fsznc-06 or Bacillus pumilus fsznc-09, but that of multiple or potentially pathogenic bacteria were lower, as compared with the control group. Tax4Fun analysis predicting the functional profiling of microbial communities showed that microbial communities in rumen or caecum were highly influential on metabolism and organism systems after feeding weanling goats with Bacillus amyloliquefaciens fsznc-06 or Bacillus pumilus fsznc-09. It was suggested that Bacillus amyloliquefaciens fsznc-06 and Bacillus pumilus fsznc-09 might be an auspicious antibiotic alternative to improve black goat growth and health by changing rumen and gut microbiota positively.

Bacillus subtilis: a universal cell factory for industry, agriculture, biomaterials and medicine

Due to its clear inherited backgrounds as well as simple and diverse genetic manipulation systems, Bacillus subtilis is the key Gram-positive model bacterium for studies on physiology and metabolism. Furthermore, due to its highly efficient protein secretion system and adaptable metabolism, it has been widely used as a cell factory for microbial production of chemicals, enzymes, and antimicrobial materials for industry, agriculture, and medicine. In this mini-review, we first summarize the basic genetic manipulation tools and expression systems for this bacterium, including traditional methods and novel engineering systems. Secondly, we briefly introduce its applications in the production of chemicals and enzymes, and summarize its advantages, mainly focusing on some noteworthy products and recent progress in the engineering of B. subtilis. Finally, this review also covers applications such as microbial additives and antimicrobials, as well as biofilm systems and spore formation. We hope to provide an overview for novice researchers in this area, offering them a better understanding of B. subtilis and its applications.

Novel Biomedical Functions of Surfactin A from Bacillus subtilis in Wound Healing Promotion and Scar Inhibition

Surfactin produced by Bacillus subtilis is a powerful biosurfactant in food, cosmetics, and pesticide industries. However, its suitability in wound healing applications is uncertain. In this article, we determined the effects of surfactin A from B. subtilis on wound healing, angiogenesis, cell migration, inflammatory response, and scar formation. The results indicated that 80.65 ± 2.03% of surfactin A-treated wounds were closed, whereas 44.30 ± 4.26% of the vehicle-treated wound areas remained open on day 7 (P < 0.05). In mechanisms, it upregulated the expression of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF), accelerated keratinocyte migration through mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signaling pathways, and regulated the secretion of proinflammatory cytokines and macrophage phenotypic switch. More attractive, surfactin A showed a seductive capability to inhibit scar tissue formation by affecting the expression of α-smooth muscle actin (α-SMA) and transforming growth factor (TGF-β). Overall, the study revealed a new function and potential of surfactin A as an affordable and efficient wound healing drug.