Acinetobacter Haemolyticus Research Articles

Identification of molecular species of polyol oils produced from soybean oil by Pseudomonas aeruginosa E03-12 NRRL B-59991

Abstract The objective of this study is to identify the chemical species of the polyol oil products produced from soybean oil by Pseudomonas aeruginosa E03-12 NRRL B-59991. We reported earlier the polyol products produced from soybean oil by Acinetobacter haemolyticus A01-35 (NRRL B-59985) ( Hou and Lin, 2013 ). The polyol oil produced by strain A01-35 were a mixture of 57 molecular species of DAG containing tri-, di-, mono-hydroxy FA and normal FA. In this study, tricaprylin was selected as internal standard for HPLC quantitative estimation of products. A CombiFlash chromatographic method was established for separation of the polyol oil products. The molecular species of the polyol oils produced from soybean oil by strain E03-12 were identified with HPLC/MS. We identified 41 derivatives of DAG, among them 32 molecular species containing one hydroxy FA and one normal FA, 8 molecular species containing two hydroxy FA without normal FA, and one molecular specie containing two normal FA without hydroxylated FA. The hydroxy FA included mono-, di- and tri-hydroxy FA. Eight molecular species of DAG containing one trihydroxy FA and 14 molecular species of DAG containing one dihydroxy FA. We have also identified 64 molecular species of TAG, among them 13 molecular species containing two hydroxy FA, 42 molecular species containing one hydroxy FA and 9 molecular species containing no hydroxylated FA. This is different from our previous findings with A. haemolyticus A01-35 which produced only DAG polyol oils. E03-12 is a better strain for developing into an industrial bioprocess.

Characterization and upregulation of bifunctional phosphoglucomutase/phosphomannomutase enzyme in an exobiopolymer overproducing strain of Acinetobacter haemolyticus

Several members of the Acinetobacter spp. produce exobiopolymer (EBP) of considerable biotechnological interest. In a previous study, we reported phosphate removal capacity of EBP produced by Acinetobacter haemolyticus. Insertional mutagenesis was attempted to develop EBP-overproducing strains of A. haemolyticus and mutant MG606 was isolated. In order to understand the underlying mechanism of overproduction, the EBP overproducing mutant MG606 was analyzed and compared with the wild type counterpart for its key EBP synthetic enzymes. The EBP produced by MG606 mutant was 650mg/L compared to 220mg/L in its wild type counterpart. Significantly high (p<0.05) levels of phosphoglucomutase/phosphomannomutase (PGM/PMM) in MG606 mutant was noted, whereas activities of other enzymes responsible for EBP synthesis showed no significant change (p>0.05). The up-regulation of PGM/PMM expression in mutant was further confirmed by real time reverse transcriptase (RT)-PCR of PGM/PMM transcripts. The optimal conditions for PGM/PMM activity were found to be 35°C and pH 7.5; PGM/PMM activity was inhibited by ions such as lithium, zinc, nickel. Further, incubation of cells with a PGM inhibitor (lithium) resulted in a concentration-dependent decrease in EBP production further confirming the role of PGM/PMM overexpression in enhanced EBP production by the mutant. Overall the results of our study indicate a key role of PGM/PMM in enhanced EBP production, as evident from enhanced enzyme activity, increased PGM/PMM transcripts and reduction in EBP synthesis by a PGM inhibitor. We envisage a potential exploitation of the insights so obtained to effectively engineer strains of Acinetobacter for overproducing phosphate binding EBP.

Acinetobacter haemolyticus MG606 produces a novel, phosphate binding exobiopolymer

The present study evaluated an extracellular, novel biopolymer produced by Acinetobacter haemolyticus MG606 for its physicochemical properties and phosphate binding mechanism. The exobiopolymer (EBP) was characterized to be majorly polysaccharide in nature consisting of 48.9kDa heteropolysaccharide composed of galactose, glucose, xylose, lyxose, allose, ribose, arabinose, mannose and fructose. Maximum phosphate binding efficiency of 25mg phosphate/g of EBP was described by Langmuir isotherm and further, the physicochemical and spectroscopic studies revealed that phosphate appeared to bind predominantly with the polysaccharide fraction, and to a relatively lesser extent to protein fraction of EBP. The electrostatic interactions with amino groups and ligand exchange with hydroxyl groups of EBP were found to be primary basis for phosphate binding mechanism. The results of this study implicate the feasibility of the EBP for commercial bioremediation processes.

Diesel Oil Degradation Potential of a Bacterium Inhabiting Petroleum Hydrocarbon Contaminated Surface Waters and Characterization of Its Emulsification Ability

AbstractDegradation of poorly water soluble hydrocarbons, like n‐alkanes and polycyclic aromatic hydrocarbons are challenged by some bacteria through emulsification of hydrocarbons by producing biosurfactants. In diesel oil bioremediation, diesel oil degrading and surfactant producing bacteria are used to eliminate these pollutants from contaminated waters. Therefore, identifying and characterizing bacteria capable of producing surfactant and degrading diesel oil are pivotal. In this study, bacteria isolated from hydrocarbon contaminated river water were screened for their potential to degrade diesel oil. Primary selection was carried out by using conventional enrichment culture technique, emulsification index measurement, gravimetric and gas chromatographic analyses of diesel oil degradation. A bacterium with 60 % emulsification index and 92 % diesel oil degradation ability in 14 days was identified as Acinetobacter haemolyticus Zn01 by 16S rRNA sequencing. A. haemolyticus Zn01 was shown to harbor both catabolic genes alkB and C23O effective in diesel oil degradation. The biosurfactant of the bacterium was also characterized in terms of surface tension, zeta potential, Fourier transform infrared spectroscopy and scanning electron microscopy. Being able to emulsify and degrade diesel oil, A. haemolyticus Zn01 seems to have high potential for the elimination of diesel oil from polluted waters.

Sugarcane bagasse as nutrient and support material for Cr(VI)-reducing biofilm

The high cost of culture growth medium is one of the problems faced in the scaling-up of biological processes involved in wastewater treatment. This makes it imperative to find a useful, cheap and easily available alternative source for culture growth medium. The present work highlights the use of sugarcane bagasse (SCB) to sustain the population of Cr(VI) reducing immobilized-biofilm system in a non-sterile condition. The locally isolated Cr(VI) reducing-resistant Acinetobacter haemolyticus was used as primary bacteria inside the sugarcane bagasse packed flow-through column and showed 92–99% Cr(VI) reduction ability during the adaptation stage using 10–100 mg/L of Cr(VI). During the column study, around 4 h (3.0 mL/min) was required to achieve complete reduction of 25 mg/L Cr(VI). The retention time increases with the increase in Cr(VI) concentration. The morphology of the immobilized cells was slightly changed in the presence of Cr(VI) as shown from the FESEM analysis. Phylogenetic analysis of the cultured bacterium from the biofilm samples suggested the dominance of Chitinophaga terrae, Laribacter hongkongensis, Ottowia thiooxydans, Rhizobium cellulosilyticum, Candidate division OP10, Pedobacter sp. as well as uncultured bacterium. Overall, sugarcane bagasse may be used as an excellent alternative and cost-effective growth medium for cultivation of A. haemolyticus as well as support material in a packed-bed Cr(VI) reduction system.

Interaction of rhizobacterial strains for growth improvement of Crocus sativus L. under tissue culture conditions

The co-cultivation of tissue explants with beneficial microbes induces numerous developmental and metabolic alterations in the resulting plantlets conferring enhanced tolerance to abiotic and biotic stresses. In the present study we have co-cultivated plant growth promoting rhizobacteria (PGPR) exhibiting multiple plant growth promoting activities with the in vitro raised saffron cormlets for evaluating various morphogenetic responses like proliferation, germination and weight increment of cormlets. The results obtained indicate the significant effect of Pseudomonas sp., Bacillus subtilis and Pantoea sp. in weight increment of cormlets. Proliferation of cormlets was also significantly improved with Pantoea sp. + Bacillus subtilus + Pseudomonas sp. on MS liquid medium. Similarly, the co-cultivation with Acinetobacter haemolyticus, Accintobacter lwoffii and Pantoea sp. resulted in 100 % germination of cormlets. The root system of cormlets was found denser and thicker than the control cormlets. However, rhizobacterial cormlets exhibited lower values of root length than non-treated cormlets. This study represents earliest report across the globe with suitable and reproducible protocol for corm development through PGPRs.

Determination of Chromium(VI) Reduction by Acinetobacter haemolyticus using X-ray Absorption Fine Structure Spectroscopy

Several types of microorganisms have been reported to reduce Cr(VI) to the less toxic Cr(III) via enzymatic reactions. The main purpose of this study is to determine the reduction of Cr(VI) by a locally isolated bacterium, Acinetobacter haemolyticus (A. haemolyticus) using the x-ray absorption fine structure (XAFS) spectroscopy. XAFS analysis consisted of both the x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectra. XANES spectra of the rinsed Cr(VI)-laden A. haemolyticus biomass indicated that chromium was only present in the form of Cr (III). The nearest atoms coordinated to Cr(III) were oxygens in an octahedral geometry. The longer Cr-O bond lengths (~1.97 Å) obtained from the EXAFS spectra corroborated the presence of chromium as Cr(III) bonded to oxygen. These findings demonstrate the ability of A. haemolyticus to reduce Cr(VI) to Cr(III) that was bound to oxygen atoms of the ligands in A. haemolyticus.

Characterization of plasmids in extensively drug-resistant acinetobacter strains isolated in India and Pakistan.

The blaNDM-1 gene is associated with extensive drug resistance in Gram-negative bacteria. This probably spread to Enterobacteriaceae from Acinetobacter spp., and we characterized plasmids associated with blaNDM-1 in Acinetobacter spp. to gain insight into their role in this dissemination. Four clinical NDM-1-producing Acinetobacter species strains from India and Pakistan were investigated. A plasmid harboring blaNDM-1, pNDM-40-1, was characterized by whole-genome sequencing of Acinetobacter bereziniae CHI-40-1 and comparison with related plasmids. The presence of similar plasmids in strains from Pakistan was sought by PCR and sequencing of amplicons. Conjugation frequency was tested and stability of pNDM-40-1 investigated by real-time PCR of isolates passaged with and without antimicrobial selection pressure. A. bereziniae and Acinetobacter haemolyticus strains contained plasmids similar to the pNDM-BJ01-like plasmids identified in Acinetobacter spp. in China. The backbone of pNDM-40-1 was almost identical to that of pNDM-BJ01-like plasmids, but the transposon harboring blaNDM-1, Tn125, contained two short deletions. Escherichia coli and Acinetobacter pittii transconjugants were readily obtained. Transconjugants retained pNDM-40-1 after a 14-day passage experiment, although stability was greater with meropenem selection. Fragments of pNDM-BJ01-like plasmid backbones are found near blaNDM-1 in some genetic contexts from Enterobacteriaceae, suggesting that cross-genus transfer has occurred. pNDM-BJ01-like plasmids have been described in isolates originating from a wide geographical region in southern Asia. In vitro data on plasmid transfer and stability suggest that these plasmids could have contributed to the spread of blaNDM-1 into Enterobacteriaceae.

Production of polyol oils from soybean oil by bioprocess: results of microbial screening and identification of positive cultures

Recently we reported methods for microbial screening and production of polyol oils from soybean oil through bioprocessing (Hou and Lin, 2013). Soy-polyol oils (oxygenated acylglycerols) are important starting materials for the manufacture of polymers such as polyurethane. Currently, they are produced by a two-step chemical process involving epoxidation and subsequent opening of the oxirane ring. A total of 650 cultures isolated from soil samples collected from a biodiesel plant in Iowa and from soil and water samples collected from Peoria, IL were screened for the production of polyol oil from soybean oil. Out of these 650 cultures screened, 50 cultures were positive for converting soybean oil to two product groups: diacylglycerol polyol oil (polyol DAGs) and diacylglycerol (DAD) with normal fatty acids. These two product groups can be separated by a two-solvent system TLC. In this study, we identified the 11 most active of these positive cultures using 16S rRNA gene analysis. The 11 strains investigated were found to be bacterial and no active yeast strains were found in the present study. Phylogenetic analysis identified two strains A01-35 and E03-25 as Acinetobacter haemolyticus, a single strain was identified as Pseudomonas aeruginosa, the other active strains were identified as Pseudomonas protegens.

Acinetobacter gandensis sp. nov. isolated from horse and cattle.

We previously reported the presence of an OXA-23 carbapenemase in an undescribed species of the genus Acinetobacter isolated from horse dung at the Faculty of Veterinary Medicine, Ghent University, Belgium. Here we include six strains to corroborate the delineation of this taxon by phenotypic characterization, DNA-DNA hybridization, 16S rRNA gene and rpoB sequence analysis, % G+C determination, MALDI-TOF MS and fatty acid analysis. The nearly complete 16S rRNA gene sequence of strain UG 60467(T) showed the highest similarities with those of the type strains of Acinetobacter bouvetii (98.4 %), Acinetobacter haemolyticus (97.7 %), and Acinetobacter schindleri (97.2 %). The partial rpoB sequence of strain UG 60467(T) showed the highest similarities with 'Acinetobacter bohemicus' ANC 3994 (88.6 %), A. bouvetii NIPH 2281 (88.6 %) and A. schindleri CIP 107287T (87.3 %). Whole-cell MALDI-TOF MS analyses supported the distinctness of the group at the protein level. The predominant fatty acids of strain UG 60467(T) were C12 : 0 3-OH, C12 : 0, C16 : 0, C18 : 1ω9c and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH). Strains UG 60467(T) and UG 60716 showed a DNA-DNA relatedness of 84 % with each other and a DNA-DNA relatedness with A. schindleri LMG 19576(T) of 17 % and 20 %, respectively. The DNA G+C content of strain UG 60467(T) was 39.6 mol%. The name Acinetobacter gandensis sp. nov. is proposed for the novel taxon. The type strain is UG 60467(T) ( = ANC 4275(T) = LMG 27960(T) = DSM 28097(T)).

Microbial Ecology of Thailand Tsunami and Non-Tsunami Affected Terrestrials

The effects of tsunamis on microbial ecologies have been ill-defined, especially in Phang Nga province, Thailand. This ecosystem was catastrophically impacted by the 2004 Indian Ocean tsunami as well as the 600 year-old tsunami in Phra Thong island, Phang Nga province. No study has been conducted to elucidate their effects on microbial ecology. This study represents the first to elucidate their effects on microbial ecology. We utilized metagenomics with 16S and 18S rDNA-barcoded pyrosequencing to obtain prokaryotic and eukaryotic profiles for this terrestrial site, tsunami affected (S1), as well as a parallel unaffected terrestrial site, non-tsunami affected (S2). S1 demonstrated unique microbial community patterns than S2. The dendrogram constructed using the prokaryotic profiles supported the unique S1 microbial communities. S1 contained more proportions of archaea and bacteria domains, specifically species belonging to Bacteroidetes became more frequent, in replacing of the other typical floras like Proteobacteria, Acidobacteria and Basidiomycota. Pathogenic microbes, including Acinetobacter haemolyticus, Flavobacterium spp. and Photobacterium spp., were also found frequently in S1. Furthermore, different metabolic potentials highlighted this microbial community change could impact the functional ecology of the site. Moreover, the habitat prediction based on percent of species indicators for marine, brackish, freshwater and terrestrial niches pointed the S1 to largely comprise marine habitat indicating-species.

Isolation, identification and characterization of highly tellurite-resistant, tellurite-reducing bacteria from Antarctica

The tellurium oxyanion, tellurite, is extremely noxious to most living organisms. Its toxicity has been mainly related to the generation of reactive oxygen species (ROS) as well as to an unbalancing of the thiol:redox buffering system. Nevertheless, a few bacteria are capable of thriving at high tellurite concentrations. One mechanism of resistance is the enzymatic and non-enzymatic reduction of tellurite to the less toxic elemental tellurium. This reduction generates nano- to micrometric tellurium crystals that display different shapes and sizes.To date, a very limited number of highly tellurite-resistant and tellurite-reducing bacterial species are available from international culture collections. In this work, we decided to look for tellurite-reducing bacteria from an extreme environment, Antarctica. This environment exhibits a combination of several extreme factors such as high UV-radiation and desiccation and freezing conditions that impact directly on the local biodiversity. Since, as does, all these factors induce ROS formation, we hypothesized that Antarctic bacteria could also exhibit tellurite-resistance. In this context, we isolated 123 tellurite-resistant bacteria, and characterized six new tellurite-resistant and tellurite-reducing bacterial strains from samples collected in Antarctica. These strains were identified according to their 16S rRNA gene sequence as Staphylococcus hameolyticus, Staphylococcus sciuri, Acinetobacter haemolyticus, Pseudomonas lini, and two strains of Psychrobacter immobilis.The isolates display tellurite-resistance about 35- to 500-fold higher than Escherichia coli (Te-sensitive organism), and a high level of tellurite reduction which might be interesting for an application in the field of bioremediation or nanoparticle biosynthesis.

Multiplex PCR to detect the genes encoding naturally occurring oxacillinases in Acinetobacter spp.

Bacteria of the genus Acinetobacter are increasingly being isolated in hospitals and are recognized as emerging nosocomial pathogens. Species identification is difficult and there is a need for simple molecular methods to differentiate between the species. Naturally occurring oxacillinase genes (blaOXA) have been identified in several Acinetobacter species and their detection by PCR can aid in species identification. The aim of this study was to develop a multiplex PCR to identify intrinsic blaOXA genes (i.e. bla(OXA-134-like), bla(OXA-211-like), bla(OXA-213-like), bla(OXA-214-like) and bla(OXA-228-like)) from Acinetobacter spp. for use as a tool for rapid species identification. Primers were designed to selectively amplify internal fragments of intrinsic blaOXA from Acinetobacter lwoffii/Acinetobacter schindleri (bla(OXA-134-like)), Acinetobacter johnsonii (bla(OXA-211-like)), Acinetobacter calcoaceticus (bla(OXA-213-like)), Acinetobacter haemolyticus (bla(OXA-214-like)) and Acinetobacter bereziniae (bla(OXA-228-like)). Multiplex PCR was performed in a total of 100 Acinetobacter isolates. Flanking primers were designed for each blaOXA subgroup and products were sequenced. All A. lwoffii, A. schindleri, A. johnsonii, A. calcoaceticus, A. haemolyticus and A. bereziniae isolates were positive for their species-specific amplicons while other Acinetobacter species were negative. Thirty blaOXA novel variants were identified; the majority of these (21/30) were from A. calcoaceticus. ISAba11 was found upstream of bla(OXA-214) in four A. haemolyticus isolates, but was not associated with carbapenem resistance. This multiplex PCR specifically detected each of the five different blaOXA subgroups. Therefore, this method has the potential to aid in the identification of these species and monitor the spread of these genes into other Acinetobacter species.

Genome sequencing and annotation of Acinetobacter haemolyticus strain MTCC 9819(T).

The genus Acinetobacter consists of 31 validly published species ubiquitously distributed in nature and primarily associated with nosocomial infection. We report the 3.4 Mb genome of Acinetobacter haemolyticus strain MTCC 9819T. The genome has a G + C content of 40.0% and includes 3 rRNA genes (5S, 23S, 16S) and 65 aminoacyl-tRNA synthetase genes.

Surface water isolates of hemolytic and non-hemolytic Acinetobacter with multiple drug and heavy metal resistance ability

Acinetobacter in surface waters are a major concern because of their rapid development of resistance to a wide range of antimicrobials and their ability to persist in these waters for a very long time. Four surface water isolates of Acinetobacter having both multidrug- and multimetal-resistant ability were isolated and identified through biochemical tests and 16S rDNA sequencing. Based on these analyses, two hemolytic isolates were affiliated with Acinetobacter haemolyticus with an accession number of X81662. The other two non-hemolytic isolates were identified as Acinetobacter johnsonii and Acinetobacter calcoaceticus and affiliated with accession numbers of Z93440 and AJ888983, respectively. The antibiotic and heavy metal resistance profiles of the isolates were determined by using 26 antibiotics and 17 heavy metals. Acinetobacter isolates displayed resistance to β-lactams, cephalosporins, aminoglycosides, and sulfonamides. The hemolytic isolates were found to show resistance to higher numbers of heavy metals than the non-hemolytic ones. Due to a possible health risk of these pathogenic bacteria, a need exists for an accurate assessment of their acquired resistance to multiple drugs and metals.

Remobilization of Trivalent Chromium and the Regeneration of In Situ Permeable Reactive Barriers during Operation

Chromium exists largely in two oxidation states, namely hexavalent chromium (Cr(VI)) which is carcinogenic and mutagenic to living organisms including humans, and tetravalent chromium (Cr(III)) which is known to be 1,000 times less toxic than Cr(VI). It is therefore desirable in most cases to reduce Cr(VI) to Cr(III). Various studies have been conducted on the Cr(VI) reduction process either in situ or ex situ. Among the suggested treatment technologies, in situ bioremediation using permeable reactive barrier as seen as the most attractive option because it can be implemented with the least impact to the environment. In this study, we evaluated the short-term operation of a Cr(VI) reducing barrier and regeneration of the biological reactive barrier to achieve continuous long-term operation. It was observed from the study that the chromium hydroxide (Cr(OH)3) produced precipitated and thus affected the porosity and hydraulic conductivity of the barrier system. It was therefore proposed to implement a regeneration process involving remobilization of precipitated Cr(OH)3 using a dilute acid (0.1 M HCl). Lowering the pH of these introduced harsh conditions which necessitated the evaluation of a possible culture shift during the regeneration phase. Microbial culture composition was evaluated using a 16S RNA finger printing method. The microbial barrier was initially inoculated with indigenous bacterial species from dried sludge. The possible microbial culture community shift in the system was evaluated using 16S rRNA fingerprinting of colonies observed from samples collected after operating the system for seven days. Phylogenic results confirmed that, after the microbial barrier system operation for seven days, the well-known Cr(VI) reducers Pseudomonas plecoglossiccida, Acinetobacter haemolyticus and Comamonas testosterone remained predominant in the culture community. The microbial barrier system successfully immobilized Cr(VI) at feed concentrations as high as 50 mg/l Cr(VI). Continuous operation of a barrier based on this technology will depend on a development of a pumping system which will ensure successful remobilisation of the metal precipitate for recovery during the regeneration process.

Plasmid pUPI126-encoded pyrrolnitrin production by Acinetobacter haemolyticus A19 isolated from the rhizosphere of wheat

An Acinetobacter species identified as A. haemolyticus A19 produces an antibiotic and the enzyme chitinase. The antibiotic produced by A. haemolyticus A19 was extracellular and inducible by co-cultivation with Klebsiella pneumoniae in the optimum ratio 2:1, respectively. pH 7, temperature 28 °C, and addition of 2% (w/v) NaCl are the most suitable environmental conditions for production and activity of the antibiotic. The antibiotic was produced in the early stationary growth phase (48 h) of A. haemolyticus A19. It has a very broad spectrum of antimicrobial activity against plant and human pathogenic bacteria and fungi. The antibiotic was extracted with ethyl acetate and purified by column chromatography with further purification by preparative thin-layer chromatography. Yield of the antibiotic was 15 mg/l. The antibiotic was active at very low concentrations, for example 50 μg/ml, and was water-soluble. It was stable at room temperature for up to 7 days. (1)H NMR analysis revealed the antibiotic was a pyrrolnitrin. It was found that pyrrolnitrin production by A. haemolyticus A19 was encoded by plasmid pUPI126 of molecular weight 25.7 kb. Plasmid pUPI126 was transferred to E. coli HB101 at a frequency of 5 × 10(-5) per μg DNA. It was also conjugally transformed to E. coli HB101 rif (r) mutants at a frequency of 5.9 × 10(-8) per recipient cell. Plasmid pUPI126 was 100% stable in Acinetobacter and 95% stable in E. coli HB101. Transconjugants and transformants both produced the antibiotic. This is the first report of plasmid-mediated pyrrolnitrin production by A. haemolyticus A19 isolated from wheat rhizosphere.

원유 내 내냉성 미생물의 계절별, 지역별 분포 및 동정

To investigate the distribution of psychrotrophic bacteria, raw milk was collected from farms in nine different regions located around Kyunggi province in South Korea at four different seasons. Psychrotrophic counts were higher in winter than in other seasons as 3.0×10 4 CFU/mL (p<0.05). Among nine regions, the population in raw milk sampled from B region was in significantly greater numbers and those from C and D province were in significantly lower numbers than any other regions, 2.4×10 5 CFU/mL and 8.7×10 3 CFU/mL, respectively (p<0.05). In addition, among 706 bacterial isolates, the predominant class was Gamma-proteobacteria (81.02%) and genus was Pseudomonas (32.34%), especially Pseudomonas fluorescens (39.46%). Compared to the regional predominance, Acinetobacter johnsonii in A region, Pseudomonas fluorescens in B region, Enterobacter amnigenus in C region, Psychrobacter maritimus in D region, Acinetobacter johnsonii in E region, Acinetobacter haemolyticus in F region, Pseudomonas fluorescens in G region, Acinetobacter jounsonii in H region, and Pseudomonas mucidolens in I region were found.

Cr(VI) reduction in naturally rich growth medium and sugarcane bagasse by Acinetobacter haemolyticus

The potential of agricultural waste as substitute for rich-growth medium for bacteria during Cr(VI) reduction was investigated using the locally isolated Cr(VI) resistant-reducing strain of Acinetobacter haemolyticus and sugarcane bagasse. A. haemolyticus showed higher resistance to 100 mg/L Cr(VI) in Luria Bertani (>1010 CFU/mL) compared to sugarcane bagasse (106 CFU/mL). Higher Cr(VI) reduction by the SCB-immobilized bacteria (>90%) compared to in LB only (around 25%) clearly indicated the role of SCB in carrying out abiotic reduction of Cr(VI) as well as Cr(VI) adsorption. Nevertheless, Cr(III) was detected on the bacterial surface using Electron Spin Resonance (ESR) and electron microscopy (FESEM–EDX) analysis. The Cr(III) deposition occurred probably via complex formation with either carboxyl, hydroxyl or amide groups present on the bacterial cells surface as suggested from the FT-IR analysis. TEM analysis further showed Cr distribution at the membrane and cytosolic fractions. This work clearly demonstrated the role of bacteria in reducing Cr(VI) to Cr(III) as well as the potential of using agricultural waste material such as SCB to carry out abiotic Cr(VI) reduction.

Identification and characterization of a cluster of genes involved in biosynthesis and transport of acinetoferrin, a siderophore produced by Acinetobacter haemolyticus ATCC 17906T

Acinetobacter haemolyticus ATCC 17906(T) is known to produce the siderophore acinetoferrin under iron-limiting conditions. Here, we show that an operon consisting of eight consecutive genes, named acbABCD and actBCAD, participates in the biosynthesis and transport of acinetoferrin, respectively. Transcription of the operon was found to be iron-regulated by a putative Fur box located in the promoter region of the first gene, acbA. Homology searches suggest that acbABCD and actA encode enzyme proteins involved in acinetoferrin biosynthesis and an outer-membrane receptor for ferric acinetoferrin, respectively. Mutants defective in acbA and actA were unable to produce acinetoferrin or to express the ferric acinetoferrin receptor under iron-limiting conditions. These abilities were rescued by complementation of the mutants with native acbA and actA genes. Secondary structure analysis predicted that the products of actC and actD may be inner-membrane proteins with 12 membrane-spanning helices that belong to the major facilitator superfamily proteins. ActC showed homology to Sinorhizobium meliloti RhtX, which has been characterized as an inner-membrane importer for ferric rhizobactin 1021 structurally similar to acinetoferrin. Compared to the parental ATCC 17906(T) strain, the actD mutant displayed about a 35 % reduction in secretion of acinetoferrin, which was restored by complementation with actD, suggesting that ActD acts as an exporter of the siderophore. Finally, the actB product was significantly similar to hypothetical proteins in certain bacteria, in which genes encoding ActBCA homologues are arranged in the same order as in A. haemolyticus ATCC 17906(T). However, the function of ActB remains to be clarified.