Arthrobacter sp. Inoculation Improves Cactus Pear Growth, Quality of Fruits, and Nutraceutical Properties of Cladodes.

A study was undertaken to determine the effects of a strain of Arthrobacter sp., a Plant Growth-Promoting Bacteria (PGPB), on plant phenology and qualitative composition of Opuntia ficus-indica (L.) Mill. fruits and cladodes. The strain was inoculated in soil, and its effects on cactus pear plants were detected and compared to nontreated plants. Compared to the latter, the treatment with bacteria promoted an earlier plant sprouting (2 months before the control) and fruitification, ameliorating fruit quality (i.e., improved fresh and dry weight: + 24% and + 26%, respectively, increased total solid content by 30% and polyphenols concentrations by 22%). The quality and quantity of monosaccharides of cladodes were also increased by Arthrobacter sp. with a positive effect on their nutraceutical value. In summer, the mean values of xylose, arabinose, and mannose were significantly higher in treated compared to not treated plants (+ 3.54; + 7.04; + 4.76 mg/kg d.w. respectively). A similar trend was observed in autumn, when the cladodes of inoculated plants had higher contents, i.e., 33% xylose, 65% arabinose, and 40% mannose, respect to the controls. In conclusion, Arthrobacter sp. plays a role in the improvement of nutritional and nutraceutical properties of cactus pear plants due to its capabilities to promote plant growth. Therefore, these results open new perspectives in PGPB application in the agro-farming system as alternative strategy to improve cactus pear growth, yield, and cladodes quality, being the latter the main by-product to be utilized for additional industrial uses.

Arthrobacter caoxuetaonis sp. nov., Arthrobacter zhangbolii sp. nov. and Arthrobacter gengyunqii sp. nov., isolated from Marmota himalayana faeces from Qinghai-Tibet Plateau.

Six aerobic or facultative anaerobic, motile, Gram-stain-positive, catalase-positive and oxidase-negative strains (zg-Y453T, zg-Y324, zg-Y462T, zg-Y411, zg-Y809T and zg-Y786) were isolated from different faecal samples of Marmota himalayana from the Qinghai-Tibet Plateau. Pale yellow, round, raised and moist colonies appeared 48 h after incubation at 28 °C on brain-heart infusion plates supplemented with 5 % defibrinated sheep blood. According to the 16S rRNA gene sequence alignment, two strain pairs (zg-Y453T/zg-Y324 and zg-Y462T/zg-Y411) shared the highest similarities to Arthrobacter luteolus (99.5 and 99.2 %), and the other one (zg-Y809T/zg-Y786) to Arthrobacter citreus (99.5 %). Results of phylogenetic analysis based on the 16S rRNA gene and genome sequences showed that these six strains represented three separate species within the genus Arthrobacter. The average nucleotide identity and digital DNA-DNA hybridization values between the three novel type strains (zg-Y453T/zg-Y462T/zg-Y809T) and other known species in this genus were all below respective thresholds (70.2-81.5/19.6-24.2 %, 70.6-81.8/19.8-25.0 %, and 70.4-88.2/19.9-35.3 %). Although phylogenetically related, there were obvious chemotaxonomic and phenotypic differences: strain pair zg-Y462T/zg-Y411 had anteiso-C15 : 0 as the only major fatty acid; the three novel species had different dominant quinones, MK-8(H2) in strains zg-Y462T/zg-Y809T (74.8/81.1 %) and MK-8(H2)/MK-9(H2) (43.1/53.0 %) in zg-Y453T; similarly, the ability to reduce nitrate in strains zg-Y453T and zg-Y462T could differentiate them from zg-Y809T. All strains had diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol, but differed slightly in the types of unidentified glycolipids, phospholipids and lipids. Based on the results of these polyphasic taxonomic analyses, three novel species within the genus Arthrobacter are proposed, namely Arthrobacter caoxuetaonis sp. nov. (type strain, zg-Y453T=GDMCC 1.2809T=JCM 35173T), Arthrobacter zhangbolii sp. nov. (type strain, zg-Y462T=GDMCC 1.2880T=JCM 35170T) and Arthrobacter gengyunqii sp. nov. (type strain, zg-Y809T=GDMCC 1.2808T=JCM 35168T).

Genomic, Molecular, and Phenotypic Characterization of Arthrobacter sp. OVS8, an Endophytic Bacterium Isolated from and Contributing to the Bioactive Compound Content of the Essential Oil of the Medicinal Plant Origanum vulgare L.

Medicinal plants play an important role in the discovery of new bioactive compounds with antimicrobial activity, thanks to their pharmacological properties. However, members of their microbiota can also synthesize bioactive molecules. Among these, strains belonging to the genera Arthrobacter are commonly found associated with the plant's microenvironments, showing plant growth-promoting (PGP) activity and bioremediation properties. However, their role as antimicrobial secondary metabolite producers has not been fully explored. The aim of this work was to characterize the Arthrobacter sp. OVS8 endophytic strain, isolated from the medicinal plant Origanum vulgare L., from molecular and phenotypic viewpoints to evaluate its adaptation and influence on the plant internal microenvironments and its potential as a producer of antibacterial volatile molecules (VOCs). Results obtained from the phenotypic and genomic characterization highlight its ability to produce volatile antimicrobials effective against multidrug-resistant (MDR) human pathogens and its putative PGP role as a producer of siderophores and degrader of organic and inorganic pollutants. The outcomes presented in this work identify Arthrobacter sp. OVS8 as an excellent starting point toward the exploitation of bacterial endophytes as antibiotics sources.

Mitigation of atrazine-induced oxidative stress on soybean seedlings after co-inoculation with atrazine-degrading bacterium Arthrobacter sp. DNS10 and inorganic phosphorus-solubilizing bacterium Enterobacter sp. P1.

Atrazine toxicity is one of the limiting factors inhibiting sensitive plant growth. Previous studies showed that atrazine-degrading bacteria could alleviate atrazine toxicity. However, there is limited information on how atrazine-degrading bacteria and plant growth-promote bacteria alleviate atrazine toxicity in soybeans. Therefore, the current study aimed to explore the atrazine removal, phosphorus utilization, and the oxidative stress alleviation of atrazine-degrading bacterium Arthrobacter sp. DNS10 and/or inorganic phosphorus-solubilizing bacterium Enterobacter sp. P1 in the reduction of atrazine toxicity in soybean. The results showed that atrazine exposure to soybean seedlings led to significant inhibition in growth, atrazine removal, and phosphorus utilization. However, the co-inoculatied strains significantly increased seedlings biomass, chlorophyll a/b contents, and total phosphorus in leaves accompanied by great reduction of the atrazine-induced antioxidant enzymes activities and malonaldehyde (MDA) contents, as well as atrazine contents in soil and soybeans under atrazine stress. Furthermore, transcriptome analysis highlighted that co-inoculated strains increased the expression levels of genes related to photosynthetic-antenna proteins, carbohydrate metabolism, and fatty acid degradation in leaves. All the results suggest that the co-inoculation mitigates atrazine-induced oxidative stress on soybean by accelerating atrazine removal from soil and phosphorus accumulation in leaves, enhancing the chlorophyll contents, and regulating plant transcriptome. It may be suggested that co-inoculation of atrazine-degrading bacteria and inorganic phosphorus-solubilizing bacteria can be used as a potential method to alleviate atrazine toxicity to the sensitive crops.

A highly efficient method with low energy and water consumption in biodegradation of total petroleum hydrocarbons of oily sludge.

The hydrocarbons in petroleum sludge are environmental pollutants. It is crucial to eliminate this type of pollution. In this study, a comprehensive and operational study has been conducted on the total petroleum hydrocarbons (TPH) biodegradation in oily sludge. The experiments were performed in a semi-solid phase by two degrader bacterium, Arthrobacter citreus and Rhodococcus jostii, and they were compared with the slurry phase. Solid samples were prepared in three mixing modes of oily sludge with clay. Experiments were conducted by semi-solid bioreactors and other methods on samples contaminated with petroleum hydrocarbons. The performance of the semi-solid bioreactor for the removal of clay-free oily sludge samples showed the best results, in which biodegradation of TPH was 90.33%. GC analyses were conducted on samples before and after biodegradation. It was observed that the contaminants were decomposed uniformly by the microorganisms, except for a combination with a large peak in 12 min. For the best case, the GC-MS test was performed before and after biodegradation. Compounds with a high concentration in the sludge were significantly reduced. Only one heavy aromatic compound was detected in 51.628 min, which decomposed quite slowly and produced a large peak. It was found that 78.2% of the compounds were removed completely.

A review on Arthrobacter sp. lipase: A versatile biocatalyst for the kinetic resolution to access enantiomerically pure/enriched compounds.

Over the last few years, there has been a dramatic increase in the number of reports related to Arthrobacter sp. lipase (ABL:MTCC No. 5125) catalyzed kinetic resolution performed in biphasic media. A strain displaying esterase/lipase activity and designated as ABL was isolated, during the course of a screening program at Indian Institute of Integrative Medicine, Jammu. Considerable research has shown that reactions catalyzed by ABL are more selective than many commercial lipases. Since new applications of this lipase are emerging, there is a great need to provide all the relevant information exclusively. This review article is an attempt to cover all the relevant reports based on isolation, purification, immobilization, and application of ABL in the biopharmaceutical sector.

Endogenous accumulation of glycine betaine confers improved low temperature resistance on transplastomic potato plants.

Glycine betaine (GB) plays a crucial role in plant response to abiotic stress, and its accumulation in chloroplasts is more effective than in the cytosol in improving the resistance of transgenic plants. Here, we report that the codA gene from Arthrobacter globiformis, which encodes a choline oxidase catalysing the conversion of choline to GB, was successfully introduced into the plastid genome of potato (Solanum tuberosum L.). Transgenic plants with plastid expression of codA showed increased tolerance to low temperature stress compared with the wild type (WT). Further studies revealed that under low temperature stress condition, transgenic plants presented a significantly higher photosynthetic performance by regulating the electron transport and energy distribution in PSII, and higher antioxidant enzyme activities and lower O2- and H2O2 accumulation than did the WT plants. A higher expression of the COR genes was also observed in transgenic plants. Our results suggest that chloroplast biosynthesis of GB could be an effective strategy for the engineering of plants with increased resistance to low temperature stress.

Phosphorus and nitrogen removal by a novel phosphate-accumulating organism, Arthrobacter sp. HHEP5 capable of heterotrophic nitrification-aerobic denitrification: Safety assessment, removal characterization, mechanism exploration and wastewater treatment.

A novel phosphate-accumulating organism (PAO), Arthrobacter sp. HHEP5 was isolated from mariculture effluents. It produced no hemolysin and was susceptible to most antibiotics. It had removal efficiencies of above 99% for 1-10 mg/L phosphorus at 18-28 °C, pH 5.5-8.5, salinities 0-3%, C/N ratios 5-20, P/N ratios 0.1-0.2 and 20-260 rpm. It exhibited simultaneous aerobic phosphorus removal, nitrification and denitrification with the highest ammonium, nitrite, nitrate removal efficiencies of 99.87%, 100%, 99.37%. Phosphorus removal was accomplished by assimilating phosphate with the existence of polyphosphate kinase completely under aerobic condition. Genes involved in nitrogen removal were amplified. 99% of phosphorus and 95% of nitrogen in both mariculture and domestic wastewater were removed by HHEP5. This study provided sound methods for future screening of PAOs and new perspectives for renewed cognition of phosphorus removal process. Wide adaptation and remarkably aerobic phosphorus, nitrogen removal performances would make HHEP5 a promising candidate in wastewater treatment.

Bioremediation of soils saturated with spilled crude oil.

A desert soil sample was saturated with crude oil (17.3%, w/w) and aliquots were diluted to different extents with either pristine desert or garden soils. Heaps of all samples were exposed to outdoor conditions through six months, and were repeatedly irrigated with water and mixed thoroughly. Quantitative determination of the residual oil in the samples revealed that oil-bioremediation in the undiluted heaps was nearly as equally effective as in the diluted ones. One month after starting the experiment. 53 to 63% of oil was removed. During the subsequent five months, 14 to 24% of the oil continued to be consumed. The dynamics of the hydrocarbonoclastic bacterial communities in the heaps was monitored. The highest numbers of those organisms coordinated chronologically with the maximum oil-removal. Out of the identified bacterial species, those affiliated with the genera Nocardioides (especially N. deserti), Dietzia (especially D. papillomatosis), Microbacterium, Micrococcus, Arthrobacter, Pseudomonas, Cellulomonas, Gordonia and others were main contributors to the oil-consumption. Some species, e.g. D. papillomatosis were minor community constituents at time zero but they prevailed at later phases. Most isolates tolerated up to 20% oil, and D. papillomatosis showed the maximum tolerance compared with all the other studied isolates. It was concluded that even in oil-saturated soil, self-cleaning proceeds at a normal rate. When pristine soil receives spilled oil, indigenous microorganisms suitable for dealing with the prevailing oil-concentrations become enriched and involved in oil-biodegradation.

Discovery of a Bacterial Gene Cluster for Deglycosylation of Toxic Potato Steroidal Glycoalkaloids α-Chaconine and α-Solanine.

Potato juice is a byproduct of starch processing currently used as feed. However, potato proteins are an untapped source of high-protein food for human nutrition if harmful constituents notably glycoalkaloids (GAs) are detoxified. The two principle GAs found in potato are α-chaconine and α-solanine, both consisting of a solanidine aglycone with a carbohydrate side chain. The first step in the detoxification of these compounds is the removal of the trisaccharide. Whole-genome sequencing of a bacterial isolate, Arthrobacter sp. S41, capable of completely degrading α-chaconine and α-solanine, revealed the presence of a gene cluster possibly involved in the deglycosylation of GAs. Functional characterization confirmed the enzymatic activity of the gene cluster involved in the complete deglycosylation of both α-chaconine and α-solanine. The novel enzymes described here may find value in the bioconversion of feed proteins to food proteins suitable for human nutrition.

Accumulation of glycine betaine in transplastomic potato plants expressing choline oxidase confers improved drought tolerance.

MAIN CONCLUSION: Plastid genome engineering is an effective method to generate drought-resistant potato plants accumulating glycine betaine in plastids. Glycine betaine (GB) plays an important role under abiotic stress, and its accumulation in chloroplasts is more effective on stress tolerance than that in cytosol of transgenic plants. Here, we report that the codA gene from Arthrobacter globiformis, which encoded choline oxidase to catalyze the conversion of choline to GB, was successfully introduced into potato (Solanum tuberosum) plastid genome by plastid genetic engineering. Two independent plastid-transformed lines were isolated and confirmed as homoplasmic via Southern-blot analysis, in which the mRNA level of codA was much higher in leaves than in tubers. GB accumulated in similar levels in both leaves and tubers of codA-transplastomic potato plants (referred to as PC plants). The GB content was moderately increased in PC plants, and compartmentation of GB in plastids conferred considerably higher tolerance to drought stress compared to wild-type (WT) plants. Higher levels of relative water content and chlorophyll content under drought stress were detected in the leaves of PC plants compared to WT plants. Moreover, PC plants presented a significantly higher photosynthetic performance as well as antioxidant enzyme activities during drought stress. These results suggested that biosynthesis of GB by chloroplast engineering was an effective method to increase drought tolerance.

Enhanced biodegradation of atrazine by Arthrobacter sp. DNS10 during co-culture with a phosphorus solubilizing bacteria: Enterobacter sp. P1.

The interaction between pure culture microorganisms has been evaluated allowing for the enhanced biodegradation of various kinds of pollutants. Arthrobacter sp. DNS10 previously enriched in an atrazine-containing soil was capable of utilizing atrazine as the sole nitrogen source for growth, and Enterobacter sp. P1 is a phosphorus-solubilizing bacterium that releases various kinds of organic acids but lacks the ability to degrade atrazine. Whether strain P1 could enhance atrazine biodegradation by the degrader strain DNS10 was investigated in this experiment. Gas chromatography and high-performance liquid chromatography results showed that co-culture of both strains degraded 99.18 ±â€¯1.00% of the atrazine (initial concentration was 100 mg L-1), while the single strain DNS10 only degraded 38.57 ±â€¯7.39% after a 48 h culture, and the resulting concentration of the atrazine final metabolite cyanuric acid were 63.91 ±â€¯3.34 mg L-1 and 26.60 ±â€¯3.87 mg L-1, respectively. In addition, the expression of the atrazine degradation-related genes trzN, atzB and atzC in co-culture treatments was 6.61, 1.81 and 3.09 times that of the single strain DNS10 culture treatment. A substrates utilization test showed that the atrazine-degrading metabolites ethylamine and isopropylamine could serve as the nitrogen source to support strain P1 growth, although strain P1 cannot degrade atrazine or utilize atrazine for growth. Furthermore, the pH of the medium was significantly decreased when strain P1 utilized ethylamine and isopropylamine as the nitrogen source for growth. The results suggest that nondegrader strain P1 could promote the atrazine biodegradation when co-cultured with strain DNS10. This phenomenon is due to metabolite exchange between the two strains. Culturing these two strains together is a new biostimulation strategy to enhance the biodegradation of atrazine by culturing these two strains together.

Factors influencing pigment production by halophilic bacteria and its effect on brine evaporation rates.

The disposal of reject brine, a highly concentrated waste by-product generated by various industrial processes, represents a major economic and environmental challenge. The common practice in dealing with the large amounts of brine generated is to dispose of it in a pond and allow it to evaporate. The rate of evaporation is therefore a key factor in the effectiveness of the management of these ponds. The addition of various dyes has previously been used as a method to increase the evaporation rate. In this study, a biological approach, using pigmented halophilic bacteria (as opposed to chemical dyes), was assessed. Two bacteria, an Arthrobacter sp. and a Planococcus sp. were selected due to their ability to increase the evaporation of synthetic brine. When using industrial brine, supplementation of the brine with an iron source was required to maintain the pigment production. Under these conditions, the Planococcus sp. CP5-4 produced a carotenoid-like pigment, which resulted in a 20% increase in the evaporation rate of the brine. Thus, the pigment production capability of halophilic bacteria could potentially be exploited as an effective step in the management of industrial reject brines, analogous to the crystallizer ponds used to mine salt from sea water.

Statistical optimization of process parameters for inulinase production from Tithonia weed by Arthrobacter mysorens strain no.1.

Tithonia rotundifolia is an easily available and abundant inulin rich weed reported to be competitive and allelopathic. This weed inulin is hydrolyzed by inulinase into fructose. Response surface methodology was employed to optimize culture conditions for the inulinase production from Arthrobacter mysorens strain no.1 isolated from rhizospheric area of Tithonia weed. Initially, Plackett- Burman design was used for screening 11 nutritional parameters for inulinase production including inulin containing weeds as cost effective substrate. The experiment shows that amongst the 11 parameters studied, K2HPO4, Inulin, Agave sisalana extract and Tithonia rotundifolia were the most significant variables for inulinase production. Quantitative effects of these 4 factors were further investigated using Box Behnken design. The medium having 0.27% K2HPO4, 2.54% Inulin, 6.57% Agave sisalana extract and 7.27% Tithonia rotundifolia extract were found to be optimum for maximum inulinase production. The optimization strategies used showed 2.12 fold increase in inulinase yield (1669.45 EU/ml) compared to non-optimized medium (787 EU/ml). Fructose produced by the action of inulinase was further confirmed by spectrophotometer, osazone, HPTLC and FTIR methods. Thus Tithonia rotundifolia can be used as an eco-friendly, economically feasible and promising alternative substrate for commercial inulinase production yielding fructose from Arthrobacter mysorens strain no.1.

Production of myo-inositol from glucose by a novel trienzymatic cascade of polyphosphate glucokinase, inositol 1-phosphate synthase and inositol monophosphatase.

Myo-inositol (inositol) is important in the cosmetics, pharmaceutical and functional food industries. Here, we report a novel pathway to produce inositol from glucose by a trienzymatic cascade system involving polyphosphate glucokinase (PPGK), inositol 1-phosphate synthase (IPS) and inositol monophosphatase (IMP). The system contained three highly active enzymes, AspPPGK from Arthrobacter sp. OY3WO11, TbIPS from Trypanosoma brucei TREU927, and EcIMP from Escherichia coli. A trienzymatic cascade reaction was implemented, and the conversion ratio from glucose to inositol reached 90%, which is promising for the enzymatic synthesis of inositol without ATP supplementation.

Impact of pectin esterification on the antimicrobial activity of nisin-loaded pectin particles.

The relationship between pectin structure and the antimicrobial activity of nisin-loaded pectin particles was examined. The antimicrobial activity of five different nisin-loaded pectin particles, i.e., nisin-loaded high methoxyl pectin, low methoxyl pectin, pectic acid, dodecyl pectin with 5.4 and 25% degree of substitution were tested in the pH range of 4.0-7.0 by agar-diffusion assay and agar plate count methods. It was found that the degree of esterification of carboxyl group of galacturonic acid in pectin molecule is important for the antimicrobial activity of nisin-loaded pectin particles. Nisin-loaded particles prepared using pectic acid or the pectin with low degree of esterification exhibit higher antimicrobial activity than nisin-loaded high methoxyl pectin particles. Pectins with free carboxyl groups or of low degree of esterification are the most suitable for particles preparation. Moreover, nisin-loaded pectin particles were active at close to neutral or neutral pH values. Therefore, they could be effectively applied for food preservation. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:245-251, 2017.

Increased iron-stress resilience of maize through inoculation of siderophore-producing Arthrobacter globiformis from mine.

Iron deficiency is common among graminaceous crops. Ecologically successful wild grasses from iron-limiting habitats are likely to harbour bacteria which secrete efficient high-affinity iron-chelating molecules (siderophores) to solubilize and mobilize iron. Such siderophore-producing rhizobacteria may increase the iron-stress resilience of graminaceous crops. Considering this, 51 rhizobacterial isolates of Dichanthium annulatum from iron-limiting abandoned mine (∼84% biologically unavailable iron) were purified and tested for siderophore production; and efficacy of Arthrobacter globiformis inoculation to increase iron-stress resilience of maize and wheat was also evaluated. 16S rRNA sequence analyses demonstrated that siderophore-producing bacteria were taxonomically diverse (seven genera, nineteen species). Among these, Gram-positive Bacillus (eleven species) was prevalent (76.92%). A. globiformis, a commonly found rhizobacterium of graminaceous crops was investigated in detail. Its siderophore has high iron-chelation capacity (ICC: 13.0 ± 2.4 µM) and effectively dissolutes diverse iron-complexes (FeCl3 : 256.13 ± 26.56 µM/ml; Fe2 O3 red: 84.3 ± 4.74 µM/ml; mine spoil: 123.84 ± 4.38 µM/ml). Siderophore production (ICC) of A. globiformis BGDa404 also varied with supplementation of different iron complexes. In plant bioassay with iron-deficiency sensitive species maize, A. globiformis inoculation triggered stress-associated traits (peroxidase and proline) in roots, enhanced plant biomass, uptake of iron and phosphate, and protein and chlorophyll contents. However, in iron deficiency tolerant species wheat, growth improvement was marginal. The present study illustrates: (i) rhizosphere of D. annulatum colonizing abandoned mine as a "hotspot" of siderophore-producing bacteria; and (ii) potential of A. globiformis BGDa404 inoculation to increase iron-stress resilience in maize. A. globiformis BGDa404 has the potential to develop as bioinoculant to alleviate iron-stress in maize.

Complete genome sequence of an aromatic compound degrader Arthrobacter sp. YC-RL1.

Arthrobacter sp. YC-RL1, isolated from a petroleum-contaminated soil, is capable of degrading and utilizing a wide range of aromatic compounds for growth. Here we report the complete genome sequence of strain YC-RL1, which may facilitate the investigation of environmental bioremediation and provide new gene resources for biotechnology and gene engineering.

Microorganisms in Vacuum Stored Flower Bee Pollen

Contamination with sanitary microorganisms from Enterobacteriaceae, Pseudomonadaceae, Staphylococcaceae, Micrococcaceae and Bacillaceae families in flower bee pollen from Bulgaria after one-year vacuum-packed cold storage has been found. Dried flower bee pollens intended for human consumption were with high incidence rate of contamination with Pantoea sp. (P. agglomerans and P. agglomerans bgp6) (100%), Citrobacter freundii (47%), Proteus mirabilis (31.6%), Serratia odorifera (15.8%) and Proteus vulgaris (5.3%). Bee pollens were also positive for the culture of microorganisms from Staphylococcaceae, Micrococcaceae and Bacillaceae families: Staphylococcus hominis subsp hominis, Staphylococcus epidermidis, Arthrobacter globiformis, Bacillus pumilis, Bacillus subtilis and Bacillus amyloliquefaciens. It was concluded that, if consumed directly, the vacuum-packed cold stored dried bee pollen, harvested according hygienic requirements from bee hives in industrial pollution-free areas without intensive crop production, is not problem for healthy human.

The effect of uranium on bacterial viability and cell surface morphology using atomic force microscopy in the presence of bicarbonate ions.

Past disposal practices at nuclear production facilities have led to the release of liquid waste into the environment creating multiple radionuclide plumes. Microorganisms are known for the ability to interact with radionuclides and impact their mobility in soils and sediments. Gram-positive Arthrobacter sp. are one of the most common bacterial groups in soils and are found in large numbers in subsurface environments contaminated with radionuclides. This study experimentally analyzed changes on the bacteria surface at the nanoscale level after uranium exposure and evaluated the effect of aqueous bicarbonate ions on U(VI) toxicity of a low uranium-tolerant Arthrobacter oxydans strain G968 by investigating changes in adhesion forces and cell dimensions via atomic force microscopy (AFM). Experiments were extended to assess cell viability by the Live/Dead BacLight Bacterial Viability Kit (Molecular Probes) and quantitatively illustrate the effect of uranium exposure in the presence of varying concentrations of bicarbonate ions. AFM and viability studies showed that samples containing bicarbonate were able to withstand uranium toxicity and remained viable. Samples containing no bicarbonate exhibited deformed surfaces and a low height profile, which, in conjunction with viability studies, indicated that the cells were not viable.