Metal-resistant Bacteria Research Articles

Biorremediación de metales pesados por plumas melanizadas y no melanizadas y bacterias degradantes de plumas, resistentes a metales pesados

Heavy metals are toxic and detrimental water pollutants. The continuous discharge of cadmium (Cd) and lead (Pb) containing effluents from industries within and around residential areas is worrisome since they do not only affects human beings, but also beneficial microbes, animals andvegetation due to their mobility in aqueous ecosystem, toxicity and non-biodegradability. The aim of this study is to compare the ability of black and white feathers to adsorb Cd and Pbin two aqueous media and to isolate Cd and Pb tolerant feather-degrading bacteria that will degrade the Cd and Pb polluted feather generated. Black and white chicken feathers were used as bio-adsorbent material in two Cd and Pb containing aqueous solutions (distilled water (DW)and feather meal broth(FMB)). The sorption capacity of the feathers was obtained by atomic absorption spectrometry andgravitational methods. Cd and Pb tolerant bacterium identified Bacillus sp. was isolated from the manure of local chick and used to degrade Cd and Pb polluted feathers. Result shows that black feathers possessed higher uptake capacity of Cd and Pb in FMB and DW, suggesting the high bio-absorption capacity of feathers in FMB that than in DW. A Cd and Pb resistant feather-degrading bacteria isolated from chicken manure were able to degrade about 40% Cd polluted feathers and 30% Pb polluted white feathers in 7 days. Even though the bacterium grew faster in FMB containing Cd polluted feathers, the degradation of Cd polluted white feathers was faster than black. Hydrolysates produced after complete degradation of polluted feathers contained low concentration of heavy metals. Bioremediation of heavy metals and recalcitrant chicken feather wastes can be achieved by melanised and un-melanised feathers and metal resistant feather-degrading bacteria.

24-Epibrassinolide combined with heavy metal resistant bacteria enhancing phytoextraction of Amaranthus hypochondriacus L. in Cd-contaminated soil

The remediation efficiency of phytoextraction on heavy metal could be influenced by metal bioavailability and plant growth. Hence, we applied a synergistic intensification system with plant hormone (24-Epibrassinolide, EBR) and metal-resistant bacterium (Serratia sp. CTZ4) to enhance Cd extraction of Amaranthus hypochondriacus L. in contaminated soil. Results demonstrated that the combination of CTZ4 and EBR promoted soil microecology through decreasing soil pH, improving soil enzymatic activity (dehydrogenase, invertase, acid phosphate, urease). Besides, microbial community structure was evaluated to understand the diversity and relative abundance of microbe in soil after remediation. Moreover, the maximum extraction of Cd was 5.91 mg kg−1 and increased about 60.16 % to CK. Meanwhile, the antioxidant system (SOD, CAT activities) of plant was improved significantly as well as plants biomass increasing by 46.02 % with the combination of EBR and CTZ4. Thus, our results proved that the utilization of EBR and CTZ4 is an alternated method to enhance phytoextraction efficiency of A. hypochondriacus in Cd-contaminated soil.

The influence on biosorption potentials of metal-resistant bacteria Enterobacter sp. EG16 and Bacillus subtilis DBM by typical red soil minerals

Due to the inevitable interaction between bacteria and soil minerals, whether bacteria could exert the excepted functions in the soil is yet to be confirmed and how minerals affect biosorption potential is needed to be investigated. The purposes of this study were to explore the adsorption behavior and mechanism of metal-resistant bacteria attaching to typical red soil minerals under different conditions and to discuss whether biosorption potential would be altered after the addition of functional bacteria to soil. Here, we tested equilibrium adsorption along with zeta potential analysis, scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and desorption to investigate the adsorption of two metal-resistant bacteria (Gram-negative Enterobacter sp. EG16 and Gram-positive Bacillus subtilis DBM) onto typical red soil minerals including goethite, kaolinite, and gibbsite under different environmental factors. We found that the minerals adsorbed more EG16 cells than DBM, and the adsorption capacities followed the sequence of goethite > kaolinite > gibbsite. Both the surfaces of bacteria and mineral were pH-dependent in our tested pH range (4.0–7.0), and the maximum adsorption was at pH 4.0. Increasing ionic strength resulted in less adsorption of bacteria onto goethite, whereas bacterial adsorption onto kaolinite was the opposite. These observations elucidated that electrostatic interaction was the dominant contributor. The adsorption conformed to the Langmuir and pseudo-second-order kinetic model implying chemical adsorption, and the result of FTIR also supported that. Desorption experiment has suggested the significant contribution of electrostatic force and the minor dominator of functional groups for bacteria–mineral combination. The results of this study indicated that electrostatic interaction was the dominant contributor to bacteria–mineral combination and functional groups coordination contributed less than 10%. This finding suggested most adhered bacteria could still provide active sites for heavy metal biosorption. Thus, although 50–90% of added functional bacteria has adhered to minerals, the bacteria–mineral combination had a limited impact on biosorption.

Metal resistant bacteria on gold particles: Implications of how anthropogenic contaminants could affect natural gold biogeochemical cycling

In Earth's near-surface environments, gold biogeochemical cycling involves gold dissolution and precipitation processes, which are partly attributed to bacteria. These biogeochemical processes as well as abrasion (via physical transport) are known to act upon gold particles, thereby resulting in particle transformation including the development of pure secondary gold and altered morphology, respectively. While previous studies have inferred gold biogeochemical cycling from gold particles obtained from natural environments, little is known about how metal contamination in an environment could impact this cycle. Therefore, this study aims to infer how potentially toxic metal contaminants could affect the structure and chemistry of gold particles and therefore the biogeochemical cycling of gold. In doing so, river sediments and gold particles from the De Kaap Valley, South Africa, were analysed using both microanalytical and molecular techniques. Of the metal contaminants detected in the sediment, mercury can chemically interact with gold particles thereby directly altering particle morphology and “erasing” textural evidence indicative of particle transformation. Other metal contaminants (including mercury) indirectly affect gold cycling by exerting a selective pressure on bacteria living on the surface of gold particles. Particles harbouring gold-tolerant bacteria with diverse metal resistant genes, such as Arthrobacter sp. and Pseudomonas sp., contained nearly two times more secondary gold relative to particles harbouring bacteria with less gold-tolerance. In conclusion, metal contaminants can have a direct or indirect effect on gold biogeochemical cycling in natural environments impacted by anthropogenic activity.

Diversity of Metal-Resistant and Tensoactive-Producing Culturable Heterotrophic Bacteria Isolated from a Copper Mine in Brazilian Amazonia

Bacterial extracellular polymeric substances (EPSs) present diverse properties of biotechnological interest, such as surface modification, metal adsorption and hydrophobic substances solubilization through surface tension reduction. Thus, there is a growing demand for new producing strains and structurally variable biomolecules with different properties. One approach for scanning this biodiversity consists of exploring environments under selective pressures. The aim of this study was to evaluate the composition of culturable heterotrophic bacterial communities from five different sites from a copper mine in the Amazon biome by an enrichment technique to obtain metal resistant bacteria (lead, arsenic, cadmium, copper and zinc) capable of producing EPSs. The bacterial densities at the sites varied from 2.42 × 103 to 1.34 × 108 NMP mL−1 and the 77 bacterial isolates obtained were classified in four divisions, β-Proteobacteria (16.88%), γ-Proteobacteria (7.29%), Firmicutes (61%) and Actinobacteria (12.98%). Bacillus, Alcaligenes, and Lysinibacillus were the most dominant among the 16 observed genera, but the relative frequency of each varied according to the sample and the metal used in the enrichment culture. 58% of the bacterial strains (45) could produce EPSs. From these, 33 strains showed emulsifying activity (E24), and 9 of them reached values higher than 49%. Only Actinomyces viscosus E3.Pb5 and Bacillus subtilis group E3.As2 reduced the medium surface tension to values lower than 35 mN m−1. It was possible to confirm the high presence of bacteria capable of producing EPSs with tensoactive properties in Amazon copper mines and the evolutionary pressure exerted by the heavy metals during enrichment. These molecules can be tested as an alternative for use in processes that involve the removal of metals, such as the bioremediation of contaminated environments.

Evaluation of biochar amendment on heavy metal resistant bacteria abundance in biosolids compost

The present investigation was design to evaluate the impact of different dosages of biochar on heavy metal resistant bacterial (HMRB) dynamic in biosolid (BS) compost. The bacterial abundance map was reveals that all the samples have 35 prominent genera and showed significant alteration of HMRB among the all biochar applied treatment. The main phyla identify in each treatments were Proteobacteria, Firmicutes and Chloroflexi, however, Pseudomonas, T78, Acinetobacter and Urebacillus were most abundant genera in all the treatment. The visualization of HMRB bio-diversity by bioinformatic tools and krona were clearly indicated a considerable difference in classification tree complexes and network analysis among the all biochar added treatments. Thus, in present study was found that HMRB like Paracoccus, Planomicrobium, Devosia and Agrobacterium viable hyper-thermo tolerant in BS compost. In addition, heat map analysis also confirmed that Proteobacteria, Firmicutes and Chloroflexi have significant correlation with physicochemical parameters.

Zeolite-supported nanoscale zero-valent iron for immobilization of cadmium, lead, and arsenic in farmland soils: Encapsulation mechanisms and indigenous microbial responses

Zeolite-supported nanoscale zero-valent iron (Z-NZVI) has great potential for metal(loid) removal, but its encapsulation mechanisms and ecological risks in real soil systems are not completely clear. We conducted long-term incubation experiments to gain new insights into the interactions between metal(loid)s (Cd, Pb, As) and Z-NZVI in naturally contaminated farmland soils, as well as the alteration of indigenous bacterial communities during soil remediation. With the pH-adjusting and adsorption capacities, 30 g kg−1 Z-NZVI amendment significantly decreased the available metal(loid) concentrations by 10.2–96.8% and transformed them into strongly-bound fractions in acidic and alkaline soils after 180 d. An innovative magnetic separation of Z-NZVI from soils followed by XRD and XPS characterizations revealed that B-type ternary complexation, heterogeneous coprecipitation, and/or concurrent redox reactions of metal(loid)s, especially the formation of Cd3(AsO4)2, PbFe2(AsO4)2(OH)2, and As0, occurred only under specific soil conditions. Sequencing of 16S rDNA using Illumina MiSeq platform indicated that temporary shifts in iron-resistant/sensitive, pH-sensitive, denitrifying, and metal-resistant bacteria after Z-NZVI addition were ultimately eliminated because soil characteristics drove the re-establishment of indigenous bacterial community. Meanwhile, Z-NZVI recovered the basic activities of bacterial DNA replication and denitrification functions in soils. These results confirm that Z-NZVI is promising for the long-term remediation of metal(loid)s contaminated farmland soil without significant ecotoxicity.

Phenotypic and genomic analysis of multiple heavy metal-resistant Micrococcus luteus strain AS2 isolated from industrial waste water and its potential use in arsenic bioremediation.

Multiple heavy metal-resistant bacterium, Micrococcus luteus strain AS2, was isolated from industrial waste water of District Sheikhupura, Pakistan. The isolated bacterium showed minimum inhibitory concentrations of 55 and 275mM against arsenite and arsenate. The bacterial strain also showed resistance against other heavy metal ions, i.e., lead, cadmium, chromium, mercury, nickel, and zinc, apart from arsenic. The optimum temperature and pH were 37°C and 7, respectively. The antioxidant enzymes such as catalase were significantly increased under arsenite stress. The increase in 43.9% of GSH/GSSG and 72.72% of non-protein thiol was determined under15mM arsenite stress. Bacterial genome was sequenced through Illumina and Nanopore and genes related to arsenic and other heavy metals were identified and blast (tblastx) on NCBI. Through scanning electron microscopy, no morphological changes were observed in bacterial cells under arsenite stress. The peaks appeared in EDX showed that there is surface adsorption of arsenite in bacterial cell while it was confirmed from Fourier transformed infrared spectroscopy analysis that there is some interaction between arsenite and functional groups present on the surface of bacterial cell. The SDS-PAGE analysis of whole-cell proteins under 15mM arsenite stress clearly revealed that there is upregulation of some proteins in ranged of 60 to 34kDa. The bioremediation efficiency (E) of bacterial biomass was 72% after 2h and 99% after 10h. The bioremediation efficiency of bacterial biomass is an indicator for the isolated bacterium to employ as a potential candidate for the amelioration of sites contaminated with arsenic.

Evaluation of the biological activity of meadow chernozem soils after the application of biochars with different pyrolysis temperatures in a model experiment

The paper aims to study the effect of fresh and aged biochar with different pyrolysis temperatures and metal resistant bacteria on the numbers of microorganisms and the dehydrogenase activity of meadow chernozem soils. The use of fresh biochar leads to an increase in the number of soil bacteria and suppression of dehydrogenase activity; after ageing biochar by incubation in the soil, dehydrogenase activity increases significantly.

Rhizoremediation of Cu(II) ions from contaminated soil using plant growth promoting bacteria: an outlook on pyrolysis conditions on plant residues for methylene orange dye biosorption

ABSTRACT Rhizoremediation is one of the most accepted, cost-effective bioremediation techniques focusing on the application of rhizospheric microorganisms in combination with plants for the remediation of organic and inorganic pollutants from the contaminated sites. This work focuses on isolation and identification of metal resistant bacteria to grow on medium with the copper ion concentration of 1500 mg/L. The resistant isolate was identified as Pantoea dispersa by a 16S rRNA sequencing. The bioaccumulation of Cu(II) ions in plant is high at the concentration of Cu(II) ion is 125 mg/L in soil. In Sphaeranthus indicus the Cu(II) ion translocation factor has expanded with an expansion of grouping of Cu(II) ion in the soil and the most extreme TF factor was acquired at the centralization of Cu(II) ion is 150 mg/L in soil. Surface morphology of biochar was characterized by Scanning Electron Microscopy (SEM) analysis. The adsorption performance of biochar (Sphaeranthus indicus biomass) and mechanism for the removal of Cu(II) ion were investigated. This study resolves that pyrolysis is promising technology for the conversion of metal ion contaminated plant residues from phytoremediation into valuable products.

Isolation of heavy metal resistance bacteria from lake sediment of IIUM, Kuantan

The present study deals with isolation and identification of heavy metal resistance bacterial strains from lake sediment located within the University of International Islamic University Malaysia (IIUM) campus with the aim to assess possible heavy metal pollution of the lake and in search of bacterial strains that can be utilized for bioremediation purposes. In a total of 80 isolates were obtained and 24 isolates were randomly selected for heavy metal resistance test using the following heavy metals - chromium (Cr), nickel (Ni), copper (Cu), cobalt (Co), cadmium (Cd) and mercury (Hg). Heavy metal resistance pattern associated with IIUM lake was in the form of Cr > Ni > Cu > Co > Cd > Hg. Isolates (I3, I5, I13 and I22) that displayed high heavy metal resistance tests were identified through the 16S rRNA gene sequence. Isolates I3 and I5 were closely related to Bacillus megaterium (99%) and Bacillus cereus (98%) respectively, while Isolate I13 was highly similar to Pseudomonas stutzeri (99%) and I22 I22 fit in Staphylococcus pasteuri (99%).

Screening of Methyl Red Degrading Bacteria Isolated from Textile Effluents of Savar Area, Dhaka, Bangladesh

Physicochemical properties and metal contents of five dye-based textile effluents collected in summer and winter season, 2016 from Savar, Dhaka, Bangladesh were within the recommended acceptable limit. The average value of all physicochemical parameters was found high in summer season except turbidity. A total of 94 heavy metal resistant bacteria (46 gram positive & 48 gram negative) were isolated from textile effluent samples and among them 17 isolates were multi metal resistant. Highest tolerance level of the isolates was shown at 10 mM concentration against Pb. All the heavy metal resistant bacterial isolates were presumably grouped into 14 genera according to morphological and biochemical assay. Three isolates designated WFB3c (65.41%), WFB4g (62%) and SFB5c (60.07%) were found to potentially degrade dye as well as tolerate heavy metals. Three potential dye decolorizer isolates were screened out and most potential one (WFB3c) was identified as Proteus mirabilis according to the 16S rRNA identification. The isolated bacterial strain Proteus mirabilis would be a potential candidate for microbes based treatment to decolorize dye from textile effluents.

Root colonization by heavy metal resistant Enterobacter and its influence on metal induced oxidative stress on Cajanus cajan.

Heavy metal resistant bacterium Enterobacter sp. C1D was evaluated for cadmium (Cd) mediated exopolysaccharide production, biofilm formation and legume root colonization ability under Cd stress to alleviate metal induced stress. The plant was sensitive to Cd (IC50 3-4μg mL-1 ), whereas the bacterium showed high Cd tolerance (MIC99 120 μg mL-1 ). Confocal laser scanning microscopy of the Cajanus cajan roots showed heavy loads of green fluorescence protein labelled Enterobacter sp. C1D on the surface of plant root, specifically at the point of root hair/lateral root formation along with cortex, even under metal stress. The root colonizing ability of Enterobacter sp. C1D was not affected by the presence of Rhizobium and the bacteria could be observed after 30 days of incubation in soil. Various plant growth parameters, antioxidant metabolites and oxidative stress indicator were significantly influenced by bacterial treatment, which, overall, reduced the adverse effect of Cd. Heavy metal tolerant bacteria may be a good choice for the development of biofertilizers and may work well with the native soil microbes such as Rhizobium under the metal polluted soil. © 2019 Society of Chemical Industry.

Heavy Metal Immobilization Potential of Indigenous Bacteria Isolated from Gold Mine Tailings

Chemical precipitation, oxidation/reduction, filtration, ion-exchange, reverse osmosis, membrane technology, evaporation and electrochemical treatment as remediation technologies have various shortcomings which have fueled the search for more environmentally friendly and cost-effective methods of remediating heavy metal contaminated environments. Indigenous bacteria in heavy metal contaminated sites present a possible solution to this concern. This study assessed the potential of indigenous heavy metal resistant bacteria as immobilization agents of Pb, Ni and Zn in Au mine tailings. Tailings from three abandoned Au mining environments; mine tailings A (MA), mine tailings B (MB), and Tudor shaft (TS) were collected and indigenous heavy metal resistant bacteria present in the tailings isolated. The isolated bacteria OMF 532 (E. asburiae) and OMF 003 (B. cereus) were used in bioaugmenting Ni-, Pb- and Zn-spiked tailings to determine the potential of the isolates to immobilize these metals. The immobilization potential of the isolates as determined by the difference in metal mobility in the tailings samples before and after bioaugmentation was used to assess the immobilization potential of the bacterial isolates. Mobility factor (MF) of Ni in the samples was reduced from 16.4 to 6.2, and 17.6 to 7.4 in MB and MA, respectively, reflecting a 35% decrease in Ni mobility. Lead and Zn mobility in the samples also showed a decrease of 90% and 60%, respectively, after bioaugmentation. Though MF values for Ni, Pb and Zn in the TS samples indicated low level of mobility of these elements at the site, bioaugmentation further reduced their mobility by 25–35% for Ni, 95% for Pb, and 10–30% for Zn. The results of this study show that indigenous bacteria in the tailings have the potential to reduce the bioavailable fractions of the three metals studied in the mine tailing and could be further exploited in heavy metal remediation of the sites. The study investigated the potential of indigenous bacteria to immobilize selected heavy metals in tailings samples. The highlights of the manuscript include the following:

Metal bioremediation potential of the halophilic bacterium, Halomonas sp. strain WQL9 isolated from Lake Qarun, Egypt

This study is designed to recover and characterize heavy metal resistant halophilic bacteria from Egypt in order to identify mechanisms, plasmids’ role, factors affecting lead (Pb) resistance, and screen for potential industrial and therapeutic enzyme production. Forty-five heavy metal resistant halophilic bacteria were recovered from eleven locations in Lake Qarun, Egypt. The WQL9 isolate showed high Pb resistance up to 4 mM and was resistant to other metals. The 16S rRNA gene analysis and phenotypic characteristics revealed that WQL9 strain belongs to the genus Halomonas. WQL9 growth in Pb-medium supplemented with glucose, yeast, and peptone increased significantly (p < 0.05) at 24 °C and pH 5. During the first 6 h, the lead uptake reached 94%. Transmission electron microscopy clarified that Pb nanoparticles were synthesized within the cell and accumulated on the exopolysaccharide area. The test strain exhibited esterase, lipase, amylase, and L-asparaginase activity. In conclusion, the WQL9 strain is a rapid and excellent tool for Pb bioremediation and a source of useful enzyme production.

Simultaneous immobilization of the cadmium, lead and arsenic in paddy soils amended with titanium gypsum

In situ immobilization of heavy metals in contaminated soils using industrial by-products is an attractive remediation technique. In this work, titanium gypsum (TG) was applied at two levels (TG-L: 0.15% and TG-H: 0.30%) to simultaneously reduce the uptake of cadmium (Cd), lead (Pb) and arsenic (As) in rice grown in heavy metal contaminated paddy soils. The results showed that the addition of TG significantly decreased the pH and dissolved organic carbon (DOC) in the bulk soil. TG addition significantly improved the rice plants growth and reduced the bioavailability of Cd, Pb and As. Particularly, bioavailable Cd, Pb and As decreased by 35.2%, 38.1% and 38.0% in TG-H treatment during the tillering stage, respectively. Moreover, TG application significantly reduced the accumulation of Cd, Pb and As in brown rice. Real-time PCR analysis demonstrated that the relative abundance of sulfate-reducing bacteria increased with the TG application, but not for the iron-reducing bacteria. In addition, 16S rRNA sequencing analysis revealed that the relative abundances of heavy metal-resistant bacteria such as Bacillus, Sulfuritalea, Clostridium, Sulfuricella, Geobacter, Nocardioides and Sulfuricurvum at the genus level significantly increased with the TG addition. In conclusion, the present study implied that TG is a potential and effective amendment to immobilize metal(loid)s in soil and thereby reduce the exposure risk of metal(loid)s associated with rice consumption.

Draft Genome Sequence of Heavy Metal-Resistant Aeromonas veronii CTe-01, Isolated from a Peruvian Wastewater Treatment Plant.

Here, we report a draft genome sequence of Aeromonas veronii strain CTe-01 (4.5 Mb), a hemolytic, heavy metal-resistant bacterium isolated from a wastewater treatment plant located at Cachiche, Ica, Peru. These characteristics could be used for bioremediation of contaminated environments.

Heavy Metal Resistance by Endophytic Bacteria Isolated from Guava (Psidium Guajava) and Mango (Mangifera Indica) Leaves

Heavy metal resistant bacteria are widespread in nature and their application in decontamination of polluted ecosystems is promising. In this study, ability of endophytic bacteria isolated from Psidium guajava (Guava) and Mangifera indica (Mango) for heavy metal resistance was assessed. Leaves samples form the two plants were collected and processed according to the standard laboratory practices. Heavy metals were analyzed using Atomic absorption spectrophotometer. Endophytic bacteria were isolated and identified using morphological and biochemical characteristics; heavy metal resistance was determined by plate dilution method. Heavy metal analysis revealed that the leaves samples contained considerable quantities of Manganese (Mn), Lead (Pb) and Cadmium (Cd) ranging from 1.21±1.6 mg/Kg (for Cd in Guava leaves) to 116.58±1.3 mg/Kg (for Mn in Mango leaves). A total of six bacterial species were isolated from both of the plants leaves (3 each). Guava endophytes were identified as Streptococcus sp, Staphylococcus albus and Staphylococcus seiuri whereas Staphylococcus aureus, Staphylococcus xylulose and Staphylococcus intermedius were from Mango leaves. The identified isolates were tested for ability to resist heavy metals in-vitro and were capable of showing different patterns of resistance to MnCl2, PbCl2 and CdCl2. All the endophytes were highly resistant to PbCl2 followed by MnCl2 but susceptible to CdCl2. The ability of plants and bacterial endophytes understudy to tolerate or resist heavy metals is a good indication of their phytoremediation potentials and thus, should be harnessed.

Complete Genome Sequence of Cellulomonas sp. Strain Y8, a High-GC-Content Plasmid-Free Heavy Metal-Resistant Bacterium Isolated from Farmland Soil.

We report the complete genome sequence of cadmium-resistant Cellulomonas sp. strain Y8, isolated from farmland soil. The 4.5-Mbp genome contains 4,074 genes, with an approximate GC content of 75%. This work might help in understanding how strain Y8 survives under heavy metal stress.

Roles of different humin and heavy-metal resistant bacteria from composting on heavy metal removal

This study aims to assess the roles of different humin and heavy-metal resistant bacterial community from composting on heavy metal removal. The results showed that the concentration of Cu2+, Zn2+, Ni2+, Pb2+, Cr3+ and Cd2+ decreased with adding the compost-derived humin, but the removal rates were relatively low (<30% on average). The heavy metal resistant bacteria from composting have better metal binding capacities than humin, and the combined addition of humin and bacteria could further stimulate the biosorption of heavy metals with 60–80% removal of metals and improve the diversity and biomass of bacterial community. There was obviously increased synergy between the humin from maturity phase and bacteria for metal biosorption (“1 + 1 > 2”). Structural equation modeling showed that microbial biomass and humin humification are the key factors for the biosorption of heavy metals. Combining humin from maturity phase with heavy-metal resistant bacteria was suggested to control heavy metal pollution in composts.