隐藏嗜酸菌Acidiphilium cryptum XTS的Cr(VI)还原特性及相关基因的差异表达

【目的】考察p H值、初始Cr（VI）浓度、Fe（III）的加入及氧气含量对隐藏嗜酸菌Acidiphilium cryptum XTS还原Cr（VI）的影响及其六价铬还原相关基因在不同培养条件下的差异表达。【方法】采用正交试验法L9（34）优选Cr（VI）还原最适条件;根据模式菌A.cryptum JF-5同源功能基因序列设计引物,对菌株XTS中的六价铬还原相关基因Acry₂099在不同培养条件下的基因差异表达进行分析。【结果】p H为2.9,初始Cr（VI）浓度为80 mg/L,Fe（III）浓度为100 mg/L的条件是该菌株还原Cr（VI）的最优化配合比,在该条件下处理24 h,Cr（VI）的还原率达到67.48%;从菌株XTS中成功克隆了Acry₂099基因,其序列与模式菌A.cryptum JF-5的同源功能基因序列一致性达到了99.7%;在不同p H值、初始Cr（VI）浓度及氧气含量下Acry₂099基因表达上调情况与Cr（VI）还原速率呈一致趋势,证明Acry₂099很可能参与还原Cr（VI）的代谢途径。虽然加入Fe（III）能促进Cr（VI）的还原,但是铁的加入对Acry₂099基因表达水平没有显著的影响。【结论】A.cryptum XTS对Cr（VI）的还原与p H值、初始Cr（VI）浓度、Fe（III）的存在等因素有关,较低的p H和较高的初始Cr（VI）浓度对该菌还原Cr（VI）具有促进作用。     

隐藏嗜酸菌Acidiphilium cryptum XTS的Cr(Ⅵ)还原特性及相关基因的差异表达

[目的]考察pH值、初始Cr(Ⅵ)浓度、Fe(Ⅲ)的加入及氧气含量对隐藏嗜酸菌Acidiphiliumcryptum XTS还原Cr(Ⅵ)的影响及其六价铬还原相关基因在不同培养条件下的差异表达.[方法]采用正交试验法L9(34)优选Cr(Ⅵ)还原最适条件;根据模式菌A.cryptum JF-5同源功能基因序列设计引物,对菌株XTS中的六价铬还原相关基因Acry_2099在不同培养条件下的基因差异表达进行分析.[结果]pH为2.9,初始Cr(Ⅵ)浓度为80 mg/L,Fe(Ⅲ)浓度为100 mg/L的条件是该菌株还原Cr(Ⅵ)的最优化配合比,在该条件下处理24 h,Cr(Ⅵ)的还原率达到67.48％;从菌株XTS中成功克隆了Acry 2099基因,其序列与模式菌A.cryptum JF-5的同源功能基因序列一致性达到了99.7％;在不同pH值、初始Cr(Ⅵ)浓度及氧气含量下Acry_2099基因表达上调情况与Cr(Ⅵ)还原速率呈一致趋势,证明Acry 2099很可能参与还原Cr(Ⅵ)的代谢途径.虽然加入Fe(Ⅲ)能促进Cr(Ⅵ)的还原,但是铁的加入对Acry 2099基因表达水平没有显著的影响.[结论]A.cryptumXTS对Cr(Ⅵ)的还原与pH值、初始Cr(Ⅵ)浓度、Fe(Ⅲ)的存在等因素有关,较低的pH和较高的初始Cr(Ⅵ)浓度对该菌还原Cr(Ⅵ)具有促进作用.     

Cr(Ⅵ)还原菌Microbacterium sp.BD6的分离鉴定及还原特性

【目的】从电镀厂下水道的淤泥中分离筛选Cr(Ⅵ)高效还原菌,并对其生长和还原特性进行研究,以期为Cr(Ⅵ)污染的生物修复提供优质的菌种资源和应用参考。【方法】采用富集培养法从淤泥中分离、筛选出Cr(Ⅵ)还原菌,通过生理生化及16S rRNA基因序列分析进行初步鉴定。采用单因素实验确定菌株的最佳培养条件和抵抗胁迫环境的能力,利用外加电子供体改善菌株的Cr(Ⅵ)还原能力,筛选出最佳电子供体研究对菌株还原的影响。【结果】经分离筛选得到1株Cr(Ⅵ)耐受还原菌,初步鉴定为微杆菌属(Microbacterium sp.),命名为BD6。菌株BD6适宜在中温、偏碱性的环境条件下生长,能耐受50.0 g/L NaCl的高盐环境。Mn^2+对菌种的生长表现出较高的抑制,Ni^2+、Zn^2+、Cd^2+的抑制作用较小,Cu^2)产生了一定的促进作用。Cr(Ⅵ)对BD6的最低抑菌浓度为1700 mg/L。添加甘油、果糖、乳糖、葡萄糖、丙酮酸钠作为电子供体促进了菌株对Cr(Ⅵ)的还原。选择甘油作为菌株还原Cr(Ⅵ)的最佳电子供体,无电子供体添加时菌株96 h内对100 mg/L Cr(Ⅵ)的还原率仅为69.63%,添加2 g/L的甘油菌株在36 h内的还原率达到了100%。通过加大甘油的添加量可以促进菌株对初始浓度较高Cr(Ⅵ)的还原,但要受到Cr(Ⅵ)的毒性限制。菌株的最适还原条件和最适生长条件吻合,在50.0 g/L NaCl的高盐条件和50 mg/L Cd^2+的毒性环境中,添加2 g/L的甘油,菌株对100 mg/L Cr(Ⅵ)的还原率分别为72 h 96.79%、54 h 99.86%。【结论】分离筛选得到的Microbacterium sp.BD6是一株潜在的可用于Cr(Ⅵ)污染生物还原修复的候选菌株。     

Cr(Ⅵ)还原菌Microbacterium sp.BD6的分离鉴定及还原特性

【目的】从电镀厂下水道的淤泥中分离筛选Cr(Ⅵ)高效还原菌,并对其生长和还原特性进行研究,以期为Cr(Ⅵ)污染的生物修复提供优质的菌种资源和应用参考。【方法】采用富集培养法从淤泥中分离、筛选出Cr(Ⅵ)还原菌,通过生理生化及16S rRNA基因序列分析进行初步鉴定。采用单因素实验确定菌株的最佳培养条件和抵抗胁迫环境的能力,利用外加电子供体改善菌株的Cr(Ⅵ)还原能力,筛选出最佳电子供体研究对菌株还原的影响。【结果】经分离筛选得到1株Cr(Ⅵ)耐受还原菌,初步鉴定为微杆菌属(Microbacterium sp.),命名为BD6。菌株BD6适宜在中温、偏碱性的环境条件下生长,能耐受50.0 g/L NaCl的高盐环境。Mn~(2+)对菌种的生长表现出较高的抑制,Ni~(2+)、Zn~(2+)、Cd~(2+)的抑制作用较小,Cu~(2+)产生了一定的促进作用。Cr(Ⅵ)对BD6的最低抑菌浓度为1700 mg/L。添加甘油、果糖、乳糖、葡萄糖、丙酮酸钠作为电子供体促进了菌株对Cr(Ⅵ)的还原。选择甘油作为菌株还原Cr(Ⅵ)的最佳电子供体,无电子供体添加时菌株96 h内对100 mg/L Cr(Ⅵ)的还原率仅为69.63%,添加2 g/L的甘油菌株在36 h内的还原率达到了100%。通过加大甘油的添加量可以促进菌株对初始浓度较高Cr(Ⅵ)的还原,但要受到Cr(Ⅵ)的毒性限制。菌株的最适还原条件和最适生长条件吻合,在50.0 g/L NaCl的高盐条件和50 mg/L Cd~(2+)的毒性环境中,添加2 g/L的甘油,菌株对100 mg/L Cr(Ⅵ)的还原率分别为72 h 96.79%、54 h 99.86%。【结论】分离筛选得到的Microbacterium sp. BD6是一株潜在的可用于Cr(Ⅵ)污染生物还原修复的候选菌株。     

还原六价铬细菌及其还原酶的研究

从活性污泥中筛选出的C-2苏云金芽孢杆菌,能耐受250mg/L的六价铬,并具有较好的还原能力。研究表明木糖、果糖、玉米饼粉、苹果酸、琥珀酸、柠檬酸及Cu2+、Fe2+、Ca2+离子对C-2菌的还原有积极作用,菌体的接种量影响还原的速率。C-2菌还原的最适温度为37℃,最适pH为9.0;六价铬还原酶的最适pH为7.0、温度为37℃,Co2+、Cu2+、Fe2+、DTT、NADH对酶的还原有积极影响。     

好氧反硝化细菌N6-1亚硝酸盐还原活性的研究

针对本实验室筛选得到的1株好氧反硝化细菌(Aerobic Denitrifying Bacteria)N6-1,研究了培养条件和培养基组分对菌株亚硝酸盐还原活性的影响.结果表明,其最适培养条件为30℃、摇床转速120 r/min、初始pH 8.5,分别以NaNO2和乙酸钠为唯一氮源和碳源时,最适碳氮比为12;初始NaNO2浓度为2g/L时,培养20 h后NO2- -N全部被还原,平均还原速率可达20.3 mg/L·h;1.5%NaCl和1%蛋白胨对其亚硝酸盐还原活性没有明显影响;10 L发酵罐培养24 h后菌体浓度高达1.2×1011 CFU/mL.     

铬还原菌的分离筛选及其在微生物燃料电池生物阴极中的应用

【目的】水溶性的Cr(Ⅵ)对环境及人类造成的危害是社会亟待解决的问题。Cr(Ⅵ)还原菌株的分离筛选、还原特性的分析和在微生物燃料电池中的应用为六价铬污染水体的微生物修复提供科学依据和新的方法。【方法】从黄河兰州段排污口采集样本,用平板法分离筛选获得具有Cr(Ⅵ)还原能力的菌株,并将Cr(Ⅵ)还原能力最强的LZU-26菌株应用到微生物燃料电池中,检测其产电能力和Cr(Ⅵ)还原特性。【结果】共分离得到21株具有Cr(Ⅵ)还原能力的菌株,其中LZU-26菌株Cr(Ⅵ)还原能力最强,属于Cellulosimicrobium cellilans。0.4 mmol/L初始Cr(Ⅵ)在LZU-26的作用下24 h铬还原率可达到95.89%,在48 h后达99.97%。将LZU-26运用在微生物燃料电池生物阴极,所获得的最大电压和最大功率密度分别为68 mV和6.8 W/cm~2。生物阴极Cr(Ⅵ)还原率(68.9%)也远高于化学阴极(14.7%)和对照组(2.7%)。【结论】利用Cr(Ⅵ)还原菌作为微生物燃料电池生物阴极处理含铬废水,将会是一种高效、节能和环境友好的方法。     

一组Cr(Ⅵ)还原菌群YEM001的培养优化

铬（Cr）是一种广泛应用于钢铁、鞣革、印染等领域的重要工业原料，由此而带来的Cr(Ⅵ)污染已成为我国主要重金属污染之一。YEM001是一组能有效还原污泥和垃圾渗滤液中的Cr(Ⅵ)，实现Cr(Ⅵ)污染生物修复的微生物菌群。然而菌群的扩大培养成为YEM001进一步应用的障碍。以优化菌群YEM001培养工艺条件为目标，通过单因素实验、正交实验对YEM001菌群的培养基和发酵条件进行了优化。结果显示以淀粉为碳源，YEM001能实现快速稳定的生长。优化后的YEM001菌群培养基为淀粉10 g/L，氯化铵3 g/L，硫酸镁2 g/L，酵母浸粉1 g/L。通过对搅拌转速、pH、通气等的调控，获得最佳发酵工艺条件为28 ℃、pH值 7.5、不通入空气、搅拌转速50 r/min。在该条件下，YEM001的培养液OD₆₀₀值可达1.91，且在60 h内能够完全还原100 mg/L Cr(Ⅵ)。通过成本分析，优化后每100 L培养基价格降低了38.11元，较优化前成本降低51.85%。     

厌氧条件下希瓦氏菌腐殖质还原对偶氮还原的影响

以希瓦氏菌属的3个代表种为研究对象,研究了在厌氧条件下腐殖质的存在对偶氮还原的影响。实验结果表明:3个代表菌株在厌氧条件下都有高效的偶氮还原和腐殖质还原功能,1mmol/L偶氮染料在24h内完全脱色,并且偶氮还原与电子供体氧化存在着紧密的偶联关系。腐殖质物质模式物2-磺酸蒽醌AQS在小于1~2mmol/L条件下能显著加速偶氮还原,12h就完全脱色,3mmol/L时18h完全脱色。但当浓度大于3mmol/L时则对偶氮还原产生明显抑制作用。另一腐殖质模式物2,6-双磺酸蒽醌AQDS其浓度在1~3mmol/L以内亦使脱色在12h内完成,4~6mmol/L时15h左右完成脱色。7~12mmol/L仍有一定的脱色促进作用,但随着浓度的提高,其促进作用也逐渐减弱。这说明腐殖质的确可以作为氧化还原中间体穿梭于电子供体与染料的偶氮双键之间促进偶氮还原。但当其浓度达到某一阈值时它就显出与偶氮键竞争电子的本质,从而使偶氮还原速率下降。原因在于他们的氧化还原电势的差异,导致细菌呼吸链的电子递体对腐殖质物质和偶氮键的亲和力不同,从而使不同腐殖质浓度对偶氮键还原产生了不同的影响。     

真菌还原Cr(Ⅵ)的研究

从不同来源的样品中分离筛选出几株抗Cr（Ⅵ）的真菌,他们能在含300—500mg／LK2Cr2O7的蔗糖合成培养基中生长,其中BS－1菌株抗K2Cr2O7达900mg／L．BS－1等4株真菌在含200mg／LK2Cr2O7的培养基中生长4-6d后,培养液中的Cr（Ⅵ）已全部消失。这些真菌经鉴定为青霉菌（Penicilliumsp．）BS－1和BS－3,黑曲霉（Aspergillusniger）BR-4和黄曲霉（Aspergillusflavus）BX－1。经紫外可见光扫描及化学分析证实,高毒的Cr（Ⅵ）可被真菌还原成为低毒的Cr（Ⅲ）。BS－1菌株细胞还原Cr（Ⅵ）的最适温度为30℃,最适pH7．0。葡萄糖（0．25％）对细胞还原Cr（Ⅵ）有促进作用,但高浓度的Cr（Ⅵ）则抑制细胞对Cr（Ⅵ）的还原。     

Enhancement of toxic Cr (VI), Fe,and other heavy metals phytoremediation by the synergistic combination of native Bacillus cereus strain and Vetiveria zizanioides L

Bioremediation of Cr (VI), Fe, and other heavy metals (HMs) through plant–microbes interaction is one of the efficient strategies due to its high efficiency, low cost, and ecofriendly nature. The aim of the study was to isolate, characterize, and assess the potential of rhizospheric bacteria to enhance growth and metal accumulation by the chromium hyperaccumulator Vetiveria zizanoides. The bacterial strain isolated from mine tailings was identified to be Bacillus cereus (T1B3) strain exhibited plant growth-promoting traits including, 1-aminocyclopropane-1-carboxylate deaminase, indole acetic acid, and siderophores production, nitrogen fixation, and P solubilization. Removal capacity (mg L^?1) of T1B3 strain was 82% for Cr⁺⁶ (100), 92% for Fe (100), 67% for Mn(50), 36% for Zn (50), 31% for Cd (30), 25% for Cu (30), and 43% for Ni (50) during the active growth cycle in HM-amended, extract medium. Results indicate that inoculating the native V. zizanioides with T1B3 strain improves its phytoremediation efficiency of HMs. The mineralogical characteristics of chromite ore tailings and soil were also confirmed by X-ray diffraction, Fourier Transform Infrared, scanning electron microscope–energy dispersive spectroscopy analysis.     

An Evaluation of a Technical Holding Time for the Preparation and Analysis of Hexavalent Chromium in Soils/Sediments

Chromium (Cr) is routinely measured during environmental investigations involving soils and other solid matrix sampling. Regulatory-approved analytical methods are available to extract and quantify total Cr in various environmental media. However, due to significant toxicity differences between trivalent [Cr(III)] and hexavalent [Cr(VI)] valences, it is compelling that the two can be quantitatively distinguished. SW-846 Method 3060A is an effective extraction technique for soluble and insoluble Cr(VI). Several regulatory-approved methods exist for quantitating the Cr(VI) in extracts or aqueous samples. Although a 6-month holding time for total Cr is not encumbering, investigators are challenged by the typical 24-h holding time (sample collection through analysis) for Cr(VI) in aqueous samples and the 24- to 96-h holding time range for solid matrix samples typically set by regulators. This research report addresses quantitating Cr(VI) in solid matrices. Using SW-846 Methods 3060A/7196A, a scientifically defensible basis has been established for designating a 30-day holding time for Cr(VI) extraction from solid matrices and a 7-day holding time for Cr(VI) analysis once solubilized in the alkaline digestate. The study results indicate that a 30-day holding time, from sample collection to preparation, and a 7-day holding time, from digestion to analysis, are appropriate for Cr(VI) analysis.     

Effect of Rhamnolipids on Chromium-Contaminated Kaolinite

Hexavalent chromium Cr(VI) is a common environmental pollutant that is treated by its reduction to the trivalent form Cr(III). The latter can be re-oxidized to the toxic form, Cr(VI), under specific conditions. A study was conducted on the removal of Cr(III) to eliminate the hazard imposed by its presence in soil as there has been some evidence that organic compounds can decrease its sorption. The effect of addition of negatively-charged biosurfactants (rhamnolipids) on chromium contaminated kaolinite was studied. Results showed that the rhamnolipids have the capability of extracting 25% portion of the stable form of chromium, Cr(III), from the kaolinite, under optimal conditions. The removal of hexavalent chromium was also enhanced compared to water by a factor of 2 using a solution of rhamnolipids. Results from the sequential extraction procedure showed that rhamnolipids remove Cr(III) mainly from the carbonate and oxide/hydroxide portions of the kaolinite. The rhamnolipids had also the capability of reducing close to 100% of the extracted Cr(VI) to Cr(III) over a period of 24 days. This study indicated that rhamnolipids could be beneficial for the removal or long–term conversion of chromium Cr(VI) to Cr(III).     

FTIR spectroscopy and scanning electron microscopic analysis of pretreated biosorbent to observe the effect on Cr (VI) remediation

Various chemical and physical treatments have been applied to indigenously isolated cyanobacterial strain, Lyngbya putealis HH-15, to observe the effect on chromium removal capacity. Pretreatment with hydrochloric acid (99.1%) and nitric acid (98.5%) resulted in enhanced chromium removal as compared to untreated control biosorbent (98.1%). Pretreatment with acetic acid (97.9%), methanol (97.0%), calcium chloride (96.0%), hot water (95.2%), and sodium hydroxide (93.9%) did not improve the chromium removal capacity of biosorbent. Fourier transform infrared spectrometry (FTIR) and scanning electron microscopy (SEM) analysis identified changes in biomass functionality and availability after physical and chemical modification—the results of which were in agreement with metal removal studies. In conclusion, this acid-treated biosorbent represents a suitable candidate to replace conventional removal technologies for metal-bearing wastewaters.     

含Cr(Ⅵ)电镀废水处理研究进展

铬的毒性与其存在状态有关,六价铬是电镀含铬废水中的主要特征污染物。综述了电镀废水中六价铬污染相关研究的近期进展。分析了水体中六价铬污染主要来源,介绍了水体中六价铬对水生生物的毒性研究概况,包括六价铬被水生生物吸收后在生物体内的积累和分布状况以及所导致的形态学、生物化学和超微结构上的伤害,介绍了电镀含铬废水常用的几种处理方法,包括离子交换树脂法、化学沉淀法、电化学法、吸附法等,重点介绍了生物除铬新技术的优点及其发展前景,最后阐述了代铬镀层的发展趋势,从源头减少六价铬的污染。     

两种价态铬(Ⅲ,Ⅵ)对真核酵母细胞谷胱甘肽水平影响

工业的迅猛发展使得重金属污染加剧,得到了人们的广泛关注。铬(Cr)在化工业中的广泛应用,使其成为一种主要的环境污染重金属离子。酿酒酵母是研究金属毒性最常用的生物之一。本文比较了三种铬盐(三氯化铬、三氧化铬、重铬酸钾)对酿酒酵母生长的影响,半抑制浓度的两种价态铬(Cr^3+,Cr^6+)处理酵母细胞,Cr^6+引起细胞的致死率更高。已有研究表明谷胱甘肽是胞内重要的还原剂,常用于细胞的重金属解毒,因此探究了两种价态的铬对酵母胞内谷胱甘肽水平的影响。结果显示重铬酸钾和三氧化铬浓度的升高都会引起胞内含量显著降低,而三氯化铬基本不变,过表达GSH1基因有利于提高酵母细胞对Cr^6+的抗性,但对Cr^3+没有明显效果,这说明两种价态铬在胞内生化作用方式不同,细胞应对的解毒机制也不一样。该研究对工业含铬废弃物处理和微生物治理环境污染提供了理论依据。     

六价铬对薏米人工湿地微生物群落数量的影响

通过桶栽构筑微型模拟垂直流薏米人工湿地(CAW),以1/2 Hoaglands营养液为营养源,在营养液中添加不同浓度的Cr6+(0,5,20,40,60mg/L,以K2Cr2O7配置),各浓度处理均以不种植薏米湿地(NPW)为对照,以研究铬(Cr6+)对薏米人工湿地基质真菌、细菌及放线菌群落结构数量的影响。结果表明:(1)真菌、细菌、放线菌的数量在薏米人工湿地(CAW)中明显多于无植物对照处理(NPW);(2)中低浓度(5、20mg/L)Cr6+对CAW真菌,对NPW细菌、放线菌数量有促进作用,薏米人工湿地微生物对低中浓度的Cr6+胁迫有一定的耐受能力。     

Kinetics and modeling of hexavalent chromium reduction in Enterobacter cloacae

Kinetics of bacterial reduction of toxic hexavalent chromium (chromate: CrO(4) (2-)) was investigated using batch and fedbatch cultures of Enterobacter cloacae strain HO1. In fedbatch cultures, the CrO(4) (2-) feed was controlled on the basis of the rate of pH change. This control strategy has proven to be useful for avoiding toxic CrO(4) (2-) overload. A simple mathematical model was developed to describe the bacterial process of CrO(4) (2-) reduction. In this model, two types of bacterial cells were considered: induced, CrO(4) (2-)-resistant cells and uninduced, sensitive ones. Only resistant cells were assumed to be able to reduce CrO(4) (2-). These fundamental ideas were supported by the model predictions which well approximated all experimental data. In a simulation study, the model was also used to optimize fed-batch cultures, instead of lengthy and expensive laboratory experiments. (c) 1993 John Wiley & Sons, Inc.     

Risk assessment of submicron PM-bound hexavalent chromium during wintertime

This study reports health risk assessment of PM₁-bound carcinogenic hexavalent chromium [Cr(VI)] from central part of Indo-Gangetic plain (IGP) (PM₁: particulate matter with aerodynamic diameter ≤1µm). Cr(VI) concentration has been estimated utilizing spectrophotometer with a modified novel method. Average ratio of Cr(VI)/Cr_T was 0.39 ± 0.07 (Cr_T: Total chromium) in the central IGP (Kanpur). Our study reports that mass fraction of Cr(VI) averaging at 0.39 is ～3 times higher than that assumed conventionally [Cr(VI)/Cr_T: 1/7]. Cancer risk assessment has been performed by assessing excess cancer risk (ECR) for the Cr(VI). ECR determined due to Cr(VI) was 57 and 14.3 (in one million) for adults and children, respectively. Our study suggests that risk due to Cr(VI) reported in previous studies were being underestimated by a factor of three. The Cr(VI)/Cr_T average ratio of 0.39 determined in this study was utilized to calculate risk assessment due to Cr(VI) from other locations in the IGP. Owing to large population of India (～125 million), the cancer risk due to Cr(VI) inhalation itself would become very significant. Thus, future research should focus on metal speciation of PM-bound samples from different locations to better constraint the toxicological risk assessment on a regional-to-global scale.     

Bacterial Reduction of Cr(VI) and Fe(III) in In Vitro Conditions

ABSTRACT Chemical reduction of Cr(VI) can be a strategy to detoxify toxic metals in oxidized states, whereas reduction of Fe(III) could enhance the availability of Fe in the form of Fe(II) to boost plant growth. However, it creates another problem of chemical sludge disposal. Hence, microbial conversion of Cr(VI) to Cr(III) and Fe(III) to Fe(II) is preferred over the chemical method. Out of 11 bacterial strains isolated from the rhizospheric zone of Typha latifolia growing on fly ash dump sites, four isolates were selected for the reduction of Cr(VI) and Fe(III) and were identified as Micrococcus roseus NBRFT2 (MTCC 9018), Bacillus endophyticus NBRFT4 (MTCC 9021), Paenibacillus macerans NBRFT5 (MTCC 8912), and Bacillus pumilus NBRFT9 (MTCC 8913). These strains were individually tested for survival at different concentrations of Cr(VI) and Fe(III), pH, and temperature, and then, their ability for reduction of both metals was evaluated at optimum pH 8.0 and temperature 35°C. The results indicated that NBRFT5 was able to reduce the maximum amount, 99% Cr(VI) and 98% Fe(III). Other strains also reduced these metals to different levels, but less than NBRFT5. Hence, these strains may be used for decontamination of metal-contaminated sites, particularly with Cr(VI) and Fe(III) through the reduction process.