Heavy metal-tolerant bacteria Bacillus cereus BCS1 degrades pyrethroid in a soil-plant system

Relationship between deltamethrin resistance and gut symbiotic bacteria of Aedes albopictus by 16S rDNA sequencing

BACKGROUND

Aedes albopictus is an important vector for pathogens such as dengue, Zika, and chikungunya viruses. While insecticides is the mainstay for mosquito control, their widespread and excessive use has led to the increased resistance in Ae. albopictus globally. Gut symbiotic bacteria are believed to play a potential role in insect physiology, potentially linking to mosquitoes' metabolic resistance against insecticides.

METHODS

We investigated the role of symbiotic bacteria in the development of resistance in Ae. albopictus by comparing gut symbiotic bacteria between deltamethrin-sensitive and deltamethrin-resistant populations. Adults were reared from field-collected larvae. Sensitive and resistant mosquitoes were screened using 0.03% and 0.09% deltamethrin, respectively, on the basis of the World Health Organization (WHO) tube bioassay. Sensitive and resistant field-collected larvae were screened using 5 × LC50 (lethal concentration at 50% mortality) and 20 × LC50 concentration of deltamethrin, respectively. Laboratory strain deltamethrin-sensitive adults and larvae were used as controls. The DNA of gut samples from these mosquitoes were extracted using the magnetic bead method. Bacterial 16S rDNA was sequenced using BGISEQ method. We isolated and cultured gut microorganisms from adult and larvae mosquitoes using four different media: Luria Bertani (LB), brain heart infusion (BHI), nutrient agar (NA), and salmonella shigella (SS).

RESULTS

Sequencing revealed significantly higher gut microbial diversity in field-resistant larvae compared with field-sensitive and laboratory-sensitive larvae (P < 0.01). Conversely, gut microorganism diversity in field-resistant and field-sensitive adults was significantly lower compared with laboratory-sensitive adults (P < 0.01). At the species level, 25 and 12 bacterial species were isolated from the gut of field resistant larvae and adults, respectively. The abundance of Flavobacterium spp., Gemmobacter spp., and Dysgonomonas spp. was significantly higher in the gut of field-resistant larvae compared with sensitive larvae (all P < 0.05). Furthermore, the abundance of Flavobacterium spp., Pantoea spp., and Aeromonas spp. was significantly higher in the gut of field-resistant adults compared with sensitive adults (all P < 0.05). The dominant and differentially occurring microorganisms were also different between resistant larval and adult mosquitoes. These findings suggest that the gut commensal bacteria of Ae. albopictus adults and larvae may play distinct roles in their deltamethrin resistance.

CONCLUSIONS

This study provides an empirical basis for further exploration of the mechanisms underlying the role of gut microbial in insecticide resistance, potentially opening a new prospect for mosquito control strategies.

Lead toxicity regulation via protein degradation and tetrapyrrole biosynthesis pathways in Brassica species: A comparative quantitative analysis of proteomic study

Understanding the heavy metals (HMs) tolerance mechanism is crucial for improving plant growth in metal-contaminated soil. In order to evaluate the lead (Pb) tolerance mechanism in Brassica species, a comparative proteomic study was used. Thirteen-day-old seedlings of B. juncea and B. napus were treated with different Pb(NO3)2 concentrations at 0, 3, 30, and 300 mg/L. Under 300 mg/L Pb(NO3)2 concentration, B. napus growth was significantly decreased, while B. juncea maintained normal growth similar to the control. The Pb accumulation was also higher in B. napus root and shoot compared to B. juncea. Gel-free proteomic analysis of roots revealed a total of 68 and 37 differentially abundant proteins (DAPs) in B. juncea and B. napus-specifically, after 300 mg/L Pb exposure. The majority of these proteins are associated with protein degradation, cellular respiration, and enzyme classification. The upregulated RPT2 and tetrapyrrole biosynthesis pathway-associated proteins maintain the cellular homeostasis and photosynthetic rate in B. juncea. Among the 55 common DAPs, S-adenosyl methionine and TCA cycle proteins were upregulated in B. juncea and down-regulated in B. napus after Pb exposure. Furthermore, higher oxidative stress also reduced the antioxidant enzyme activity in B. napus. The current finding suggests that B. juncea is more Pb tolerant than B. napus, possibly due to the upregulation of proteins involved in protein recycling, degradation, and tetrapyrrole biosynthesis pathway.

Novel melatonin-producing Bacillus safensis EH143 mitigates salt and cadmium stress in soybean

Recently, microorganism and exogenous melatonin application has been recognized as an efficient biological tool for enhancing salt tolerance and heavy metal detoxification in agriculture crops. Thus, the goal of this study was to isolate and evaluate a novel melatonin-producing plant growth promoting bacterium. With high-throughput whole genome sequencing, phytohormone measurements, expression profiling, and biochemical analysis, we can identify a novel PGPB that produces melatonin and unravel how it promotes soybean growth and development and protects against salt and Cd stress. We identify the melatonin synthesis pathway (tryptophan→tryptamine→serotonin melatonin) of the halotolerant (NaCl > 800 mM) and heavy metal-resistant (Cd >3 mM) rhizobacterium Bacillus safensis EH143 and use it to treat soybean plants subjected to Cd and NaCl stresses. Results show that EH143 will highly bioaccumulate heavy metals and significantly improve P and Ca2+ uptake and the K+/Na+ (93%↑under salt stress) ratio while reducing Cd uptake (49% under Cd stress) in shoots. This activity was supported by the expression of the ion regulator HKT1, MYPB67, and the calcium sensors CDPK5 and CaMK1 which ultimately led to increased plant growth. EH143 significantly decreased ABA content in shoots by 13%, 20%, and 34% and increased SA biosynthesis in shoots by 14.8%, 31%, and 48.2% in control, salt, and Cd-treated plants, upregulating CYP707A1 and CYP707A2 and PAL1 and ICS, respectively. The melatonin content significantly decreased along with a reduced expression of ASMT3 following treatment with EH143; moreover, reduced expression of peroxidase (POD) and superoxide dismutase (SOD) by 134.5% and 39% under salt+Cd stress, respectively and increased level of total amino acids were observed. Whole-genome sequencing and annotation of EH143 revealed the presence of the melatonin precursor tryptophan synthase (trpA, trpB, trpS), metal and other ion regulators (Cd: cadA, potassium: KtrA and KtrB, phosphate: glpT, calcium: yloB, the sodium/glucose cotransporter: sgIT, and the magnesium transporter: mgtE), and enzyme activators (including the siderophore transport proteins yfiZ and yfhA, the SOD sodA, the catalase katA1, and the glutathione regulator KefG) that may be involved in programming the plant metabolic system. As a consequence, EH143 treatment significantly reduced the contents of lipid peroxidation (O2-, MDA, and H2O2) up to 69%, 46%, and 29% in plants under salt+Cd stress, respectively. These findings suggest that EH143 could be a potent biofertilizer to alleviate NaCl and Cd toxicity in crops and serve as an alternative substitute for exogenous melatonin application.

Impact of Anthropogenic Activities on Microbial Community Structure in Riverbed Sediments of East Kazakhstan

Heavy metal (HMe) pollution in regions with mining and metallurgy activities is known to be a serious environmental problem worldwide. Hydrological processes contribute to the dissemination of HMes (drainage, precipitation, flow rate). The aim of the present study is to investigate the microbial community structure in ten river sediments sampled in different regions of East Kazakhstan, which are contaminated with HMes. The overall degree of sediment contamination with HMes (Cr, Cu, Zn, Pb, and Cd) was assessed using the pollution index Zc, which ranged from 0.43 to 21.6, with the highest in Ridder City (Zc = 21.6) and Ust-Kamenogorsk City, 0.8 km below the dam of the hydroelectric power station (Zc = 19.6). The tested samples considerably differed in organic matter, total carbon, nitrogen, and phosphorus content, as well as in the abundance of HMe-related functional gene families and antibiotic resistance genes. Metagenomic analysis of benthic microorganisms showed the prevalence of Proteobacteria (88.84-97.61%) and Actinobacteria (1.21-5.98%) at the phylum level in all samples. At the class level, Actinobacteria (21.68-57.48%), Betaproteobacteria (19.38-41.17%), and Alphaproteobacteria (10.0-39.78%) were the most common among the classified reads. To the best of our knowledge, this is the first study on the metagenomic characteristics of benthic microbial communities exposed to chronic HMe pressure in different regions of East Kazakhstan.

Effect of Lyoprotective Agents on the Preservation of Survival of a Bacillus cereus Strain PBG in the Freeze-Drying Process

Lyophilization is a widely employed long-term preservation method in which the bacterial survival rate largely depends on the cryoprotectant used. Bacillus cereus strain PBC was selected for its ability to thrive in environments contaminated with arsenic, lead, and cadmium, tolerate 500 ppm of free cyanide, and the presence of genes such as ars, cad, ppa, dap, among others, associated with the bioremediation of toxic compounds and enterotoxins (nheA, nheB, nheC). Following lyophilization, the survival rates for Mannitol 2.5%, Mannitol 10%, and Glucose 1% were 98.02%, 97.12%, and 96.30%, respectively, with the rates being lower than 95% for other sugars. However, during storage, for the same sugars, the survival rates were 78.71%, 97.12%, and 99.97%, respectively. In the cake morphology, it was found that the lyophilized morphology showed no relationship with bacterial survival rate. The best cryoprotectant for the PBC strain was 1% glucose since it maintained constant and elevated bacterial growth rates during storage, ensuring that the unique characteristics of the bacterium were preserved over time. These findings hold significant implications for research as they report a new Bacillus cereus strain with the potential to be utilized in bioremediation processes.