Whole-Genome Sequencing of a Multidrug-Resistant Strain: Delftia acidovorans B408.

BACKGROUND: Delftia acidovorans is distributed widely in the environment and has the potential to promote the growth of plants and degrade organic pollutants. However, it is also an opportunistic pathogen for human and many reports demonstrated that D. acidovorans has strong resistance to aminoglycosides and polymyxins. OBJECTIVE: The aim of this work was to reveal the antibiotic resistance genes and pathogenic genes in a novel conditional pathogenic strain-D. acidovorans B804, which was isolated from the radiation-polluted soil from Xinjiang Uyghur Autonomous Region, China. METHODS: The antibiotic resistance test was performed according to the Kirby-Bauer disk diffusion method and evaluated by the standards of the Clinical and Laboratory Standards Institute guidelines. The genome of D. acidovorans B804 was sequenced by a PacBio RS II and Illumina HiSeq 4000 platform in Shanghai Majorbio Biopharm Technology Co., Ltd. (Shanghai, China). RESULTS: The multidrug resistance phenotypes of D. acidovorans B804 was experimentally confirmed and its genome was sequenced. The total size of D. acidovorans B804 genome was 6,661,314 bp with a GC content of 66.73%. 403 genes associated with antibiotic resistances were predicted. Meanwhile, 89 pathogenic genes were also predicted and 17 of these genes might be capable of causing diseases to human, such as infections and salmonellosis. CONCLUSIONS: This genomic information can be used as a reference sequence for comparative genomic studies. The results provided more insights regarding the pathogenesis and drug resistance mechanism of D. acidovorans, which will be meaningful for developing more effective therapies toward D. acidovorans-related diseases.

Using Bacillus thuringiensis HM-311@hydroxyapatite@biochar beads to remediate Pb and Cd contaminated farmland soil.

Cadmium (Cd) and lead (Pb) have become serious soil contaminants in China. In this work, we immobilized B. thuringiensis HM-311 (a heavy metal resistant strain) using vinegar residue biochar and hydroxyapatite (HAP) to form BtHM-311@HAP@biochar calcium alginate beads. In aqueous solution, the beads respectively reduced 1000 mg/L Pb2+ to 14.59 mg/L and 200 mg/L Cd2+ to 5.40 mg/L within 20 h. Furthermore, the results of pot experiment showed that the BtHM-311@HAP@biochar beads reduced the bioavailability of Pb and Cd in soil. The accumulation of Pb2+ in rice decreased by 39.97% in shoots and 46.40% in roots, while that of Cd2+ decreased by 34.59 and 44.9%, respectively. Similarly, the accumulation of Pb2+ in corn decreased by 40.86% in shoots and 51.34% in roots, while that of Cd2+ decreased by 41.28 and 42.91%, respectively. The beads also increased the microbial community diversity in the rhizosphere soil. These findings indicate that BtHM-311@HAP@biochar beads may be applicable for the bioremediation of Cd- and Pb-contaminated farmland soil.

Making waves: Microbe-photocatalyst hybrids may provide new opportunities for treating heavy metal polluted wastewater.

Heavy metal contamination has received increasing attention as a growing worldwide environmental problem. Traditional remediation methods are mainly based on adsorption, precipitation and oxidation-reduction, which reduce the availability or toxicity of heavy metal ions. Microbe-photocatalyst hybrids (MPH), which behave as a semi-artificial photosynthetic system, integrate microbial cells with artificial photocatalysts for solar-to-chemical conversion. A few very recent studies indicate that MPH can be applied to treat organic contamination in water. Here, we propose a novel idea that MPH may also have great potential for solving heavy metal pollution. Heavy metals in wastewater could possibly be utilized to synthesize photocatalysts for MPH by microbial mineralization. Photo-induced electrons generated by photocatalysts in MPH can be transferred into microbial cells to promote intracellular enzymatic reductions, which allows heavy metal ions such as Cr6+ and Se4+ to be reduced and detoxified. Moreover, heavy metal ions like As3+ and Sb3+ can be used as sacrificial electron donors to maintain the continuous operation of the MPH, whereby these metal ions are simultaneously oxidized and detoxified. The excellent potential of MPH in the treatment of heavy metal-polluted wastewater is explained and a solution based on MPH is put forward as well as verified experimentally in this work. This solution can realize electron transfer between different metal ions to simultaneously remediate multiple heavy metal ions in wastewater. This finding may bring new hope for treating multiple heavy metal polluted wastewater in the future.

Root exuded low-molecular-weight organic acids affected the phenanthrene degrader differently: A multi-omics study.

As a class of highly toxic and persistent organic pollutants, polycyclic aromatic hydrocarbons (PAHs) are an increasingly urgent environmental problem. Low-molecular-weight organic acids (LMWOAs) are important factors that regulate the degradation of PAHs by plant rhizosphere microorganisms, which affect the absorption of PAHs by plant roots. However, the comprehensive mechanisms by which LMWOAs influence the biodegradation of PAHs at cellular and omics levels are still unknown. Here, we systematically analyzed the roles of citric, glutaric and oxalic acid in the PAH-degradation process, and investigated the mechanisms through which these three LMWOAs enhance phenanthrene (PHE) biodegradation by B. subtilis ZL09-26. The results showed that LMWOAs can improve the solubility and biodegradation of PHE, enhance cell growth and activity, and relieve membrane and oxidative stress. Citric acid enhanced PHE biodegradation mainly by improving the strain's cell proliferation and activity, while glutaric and oxalic acid accelerated PHE biodegradation mainly by improving the expression of enzymes and providing energy for the cells of B. subtilis ZL09-26. This study provides new insights into rhizospheric bioremediation mechanisms, which may enable the development of new biostimulation techniques to improve the bioremediation of PAHs.

Degradation of organic pollutants by intimately coupling photocatalytic materials with microbes: a review.

With the rapid development of industry and agriculture, large amounts of organic pollutants have been released into the environment. Consequently, the degradation of refractory organic pollutants has become one of the toughest challenges in remediation. To solve this problem, intimate coupling of photocatalysis and biodegradation (ICPB) technology, which allows the simultaneous action of photocatalysis and biodegradation and thus integrates the advantages of photocatalytic reactions and biological treatments, was developed recently. ICPB consists mainly of porous carriers, photocatalysts, biofilms, and an illuminated reactor. Under illumination, photocatalysts on the surface of the carriers convert refractory pollutants into biodegradable products through photocatalytic reactions, after which these products are completely degraded by the biofilms cultivated in the carriers. Additionally, the biofilms are protected by the carriers from the harmful light and free radicals generated by the photocatalyst. Compared with traditional technologies, ICPB remarkably improves the degradation efficiency and reduces the cost of bioremediation. In this review, we introduce the origin and mechanisms of ICPB, discuss the development of reactors, carriers, photocatalysts, and biofilms used in ICPB, and summarize the applications of ICPB to treat organic pollutants. Finally, gaps in this research as well as future perspectives are discussed.

Whole genome sequencing of a multidrug-resistant Bacillus thuringiensis HM-311 obtained from the Radiation and Heavy metal-polluted soil.

OBJECTIVES: Bacillus thuringiensis (BT) is distributed widely in the environment and utilised frequently for its highly specific toxins to target insect. However, BT is potentially pathogenic due to the high similarity between BT and Bacillus anthracis (BA). Meanwhile, there are reports that heavy metal pressure can promote the proliferation of antibiotic resistance in microorganisms through the co-selection of metal resistance genes (MRGs) and antibiotic resistance genes (ARGs). The aim of this work was revealed the MRGs and ARGs in a novel heavy metal tolerant and drug-resistant strain - B. thuringiensis HM-311, which was isolated from radiation and heavy metal-contaminated soil in Xinjiang (China). METHODS: The genome of B. thuringiensis HM-311 was sequenced using a PacBio RS II platform and Illumina HiSeq 4000 platform at the Beijing Genomics Institute (BGI, Shenzhen, China). RESULTS: The total size of B. thuringiensis HM-311 genome was 6,019,481bp with a GC content of 35.85%. 134 genes related to antibiotics resistance and 75 genes related to heavy metal resistance were predicted in the B. thuringiensis HM-311 genome, the main ARGs and MRGs were discussed. Moreover, 30 verified virulence factor genes and 297 predicted virulence factor genes were annotated in the B. thuringiensis HM-311 genome. CONCLUSIONS: This genome can be used as a reference sequence for comparative genomic studies, elucidating antibiotic resistance development and the relationship between antibiotic resistance genes and heavy metal resistance genes in B. thuringiensis.