Rhodococcus phenolicus sp. nov., a novel bioprocessor isolated actinomycete with the ability to degrade chlorobenzene, dichlorobenzene and phenol as sole carbon sources

Efficient and low-energy degradation of chlorobenzene via catA-mediated cleavage and bedC1 docking in a novel Burkholderia stabilis TF-2

In this study, a novel strain Burkholderia stabilis TF-2 capable of assimilatory and co-metabolic degradation of chlorobenzenes was obtained. The interaction between chlorobenzene (CB) and target enzymes, as well as the metabolic pathways in TF-2, were elucidated using multi-omics and molecular docking techniques. Results of degradation experiments indicated that TF-2 assimilated CB at a rate of 0.22-0.66 mg·gcell-1·h-1 in concentrations of 20-200 mg L-1. Additionally, TF-2 also used sodium succinate and sodium citrate as substrates to co-metabolize CB, with degradation rates of 0.26-2.00 and 0.31-1.72 mol·gcell-1·h-1, respectively. Whole-genome sequencing revealed over 18 novel genes associated with aromatic hydrocarbon degradation in TF-2. Transcriptomic analysis showed that CB induced the high expression of 119 genes involved in CB metabolism and late mineralization. The significant up-regulation of the bedC1 (encoding a ring-hydroxylated dioxygenase), CatA (chlorocatechol 1,2-dioxygenase), pcaJ (3-oxoadipate CoA-transferase alpha subunit) and fadA (acetyl-CoA acyltransferase) genes facilitated CB metabolism. Based on these findings, a metabolic pathway for CB was constructed, with the key step involving ortho cleavage of the aromatic ring under the action of the catA gene. Furthermore, molecular docking revealed that CB bound to bedC1 with -4.5 kcal mol-1 through hydrophobic bonds, π-stacking, and a halogen bond. These results provide strong support for development of efficient strains to enhance the removal of chlorinated organic compounds.

Efficient biodegradation of chlorobenzene via monooxygenation pathways by Pandoraea sp. XJJ-1 with high potential for groundwater bioremediation

Chlorobenzene (CB), extensively used in industrial processes, has emerged as a significant contaminant in soil and groundwater. The eco-friendly and cost-effective microbial remediation has been increasingly favored to address this environmental challenge. In this study, a degrading bacterium was isolated from CB-contaminated soil at a pesticide plant, identified as Pandoraea sp. XJJ-1 (CCTCC M 2021057). This strain completely degraded 100 mg·L-1 CB and showed extensive degradability across a range of pH (5.0-9.0), temperature (10-37 °C), and CB concentrations (100-600 mg·L-1). Notably, the degradation efficiency was 85.2% at 15 °C, and the strain could also degrade six other aromatic hydrocarbons, including benzene, toluene, ethylbenzene, and xylene (o-, m-, p-). The metabolic pathway of CB was inferred using ultraperformance liquid chromatography, gas chromatography-mass spectrometry, and genomic analysis. In strain XJJ-1, CB was metabolized to o-chlorophenol and 3-chloroxychol by CB monooxygenase, followed by ortho-cleavage by the action of 3-chlorocatechol 1,2-dioxygenase. Moreover, the presence of the chlorobenzene monooxygenation pathway metabolism in strain XJJ-1 is reported for the first time in Pandoraea. As a bacterium with low-temperature resistance and composite pollutant degradation capacity, strain XJJ-1 has the potential application prospects in the in-situ bioremediation of CB-contaminated sites.

Reduction characteristic of chlorobenzene by a newly isolated Paenarthrobacter ureafaciens LY from a pharmaceutical wastewater treatment plant

A highly efficient chlorobenzene-degrading strain was isolated from the sludge of a sewage treatment plant associated with a pharmaceutical company. The strain exhibited a similarity of over 99.9% with multiple strains of Paenarthrobacter ureafaciens. Therefore, the strain was suggested to be P. ureafaciens LY. This novel strain exhibited a broad spectrum of pollutant degradation capabilities, effectively degrading chlorobenzene and other organic pollutants, such as 1, 2, 4-trichlorobenzene, phenol, and xylene. Moreover, P. ureafaciens LY co-metabolized mixtures of chlorobenzene with 1, 2, 4-trichlorobenzene or phenol. Evaluation of its degradation efficiency showed that it achieved an impressive degradation rate of 94.78% for chlorobenzene within 8 h. The Haldane-Andrews model was used to describe the growth of P. ureafaciens LY under specific pollutants and its concentrations, revealing a maximum specific growth rate (μmax ) of 0.33 h-1 . The isolation and characterization of P. ureafaciens LY, along with its ability to degrade chlorobenzene, provides valuable insights for the development of efficient and eco-friendly approaches to mitigate chlorobenzene contamination. Additionally, investigation of the degradation performance of the strain in the presence of other pollutants offers important information for understanding the complexities of co-metabolism in mixed-pollutant environments.

Rhodococcus yananensis sp. nov., a novel denitrification actinobacterium isolated from microbial fermentation bed material from a pig farm

An opaque, pink-coloured, gram-positive, aerobic bacteria (designated as FBM22-1T), was isolated from microbial fermentation bed material from a pig farm in northwestern China. Optimal growth occurred at 30–37 °C, pH 7.0 and with 0.5 % NaCl (w/v). The strain had nitrification and denitrification functions. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the novel isolate belonged to the genus Rhodococcus . Strain FBM22-1T was closely related to Rhodococcus zopfii NBRC 100606T and Rhodococcus rhodochrous NBRC 16069T, with 16S rRNA gene sequence similarities of 97.9 and 97.7 %, respectively. The predominant menaquinone in strain FBM22-1T was MK-8(H2). The cellular fatty acids consisted primarily of C16 : 1ω7c and/or C16 : 1 ω6c, C16 : 0 and 10-methyl C18 : 0. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and glycolipid. The G+C content of strain FBM22-1T was 68.64 mol%. Based on the phenotypic, phylogenetic and chemotaxonomic characterization results, in combination with low values of digital DNA–DNA hybridization between strain FBM22-1T and its closest neighbours, FBM22-1T represents a novel species of the genus Rhodococcus , for which the name Rhodococcus yananensis sp. nov. is proposed; the type strain is FBM22-1T (=KCTC 49502T=CCTCC AB2020275T).

Arbuscular mycorrhizal and microbial profiles of an aged phenol-polynuclear aromatic hydrocarbon-contaminated soil

Arbuscular mycorrhizal fungi (AMF) are ubiquitous, obligatory plant symbionts that have a beneficial influence on plants in contaminated environments. This study focused on evaluating the biomass and biodiversity of the AMF and microbial communities associated with Poa trivialis and Phragmites australis plants sampled at an aged site contaminated with phenol and polynuclear aromatic hydrocarbons (PAHs) and an uncontaminated control site. We analyzed the soil phospholipid fatty acid profile to describe the general structure of microbial communities. PCR-denaturing gradient gel electrophoresis with primers targeting the 18S ribosomal RNA gene was used to characterize the biodiversity of the AMF communities and identify dominant AMF species associated with the host plants in the polluted and control environments. The root mycorrhizal colonization and AMF biomass in the soil were negatively affected by the presence of PAHs and phenol, with no significant differences between the studied plant species, whereas the biodiversity of the AMF communities were influenced by the soil contamination and plant species. Soil contamination was more detrimental to the biodiversity of AMF communities associated with Ph. australis, compared to P. trivialis. Both species favored the development of different AMF species, which might be related to the specific features of their different root systems and soil microbial communities. The contaminated site was dominated by AMF generalists like Funneliformis and Rhizophagus, whereas in the control site Dominikia, Archaeospora, Claroideoglomus, Glomus, and Diversispora were also detected.

A new Rhodococcus aetherivorans strain isolated from lubricant-contaminated soil as a prospective phenol-biodegrading agent

Microbe-based decontamination of phenol-polluted environments has significant advantages over physical and chemical approaches by being relatively cheaper and ensuring complete phenol degradation. There is a need to search for commercially prospective bacterial strains that are resistant to phenol and other co-pollutants, e.g. oil hydrocarbons, in contaminated environments, and able to carry out efficient phenol biodegradation at a variable range of concentrations. This research characterizes the phenol-biodegrading ability of a new actinobacteria strain isolated from a lubricant-contaminated soil environment. Phenotypic and phylogenetic analyses showed that the novel strain UCM Ac-603 belonged to the species Rhodococcus aetherivorans, and phenol degrading ability was quantitatively characterized for the first time. R. aetherivorans UCM Ac-603 tolerated and assimilated phenol (100% of supplied concentration) and various hydrocarbons (56.2–94.4%) as sole carbon sources. Additional nutrient supplementation was not required for degradation and this organism could grow at a phenol concentration of 500 mg L⁻¹ without inhibition. Complete phenol assimilation occurred after 4 days at an initial concentration of 1750 mg L⁻¹ for freely-suspended cells and at 2000 mg L⁻¹ for vermiculite-immobilized cells: 99.9% assimilation of phenol was possible from a total concentration of 3000 mg L⁻¹ supplied at daily fractional phenol additions of 750 mg L⁻¹ over 4 days. In terms of phenol degradation rates, R. aetherivorans UCM Ac-602 showed efficient phenol degradation over a wide range of initial concentrations with the rates (e.g. 35.7 mg L⁻¹ h⁻¹ at 500 mg L⁻¹ phenol, and 18.2 mg L⁻¹ h⁻¹ at 1750 mg L⁻¹ phenol) significantly exceeding (1.2–5 times) reported data for almost all other phenol-assimilating bacteria. Such efficient phenol degradation ability compared to currently known strains and other beneficial characteristics of R. aetherivorans UCM Ac-602 suggest it is a promising candidate for bioremediation of phenol-contaminated environments.

Superior performance and mechanism of chlorobenzene degradation by a novel bacterium

A newly isolated strain was identified as Ochrobactrum sp. by 16S rRNA sequence analysis and named as ZJUTCB-1.

Current taxonomy of Rhodococcus species and their role in infections

Rhodococcus is a genus of obligate aerobic, Gram-positive, partially acid-fast, catalase-positive, non-motile, and none-endospore bacteria. The genus Rhodococcus was first introduced by Zopf. This bacterium can be isolated from various sources of the environment and can grow well in non-selective medium. A large number of phenotypic characterizations are used to compare different species of the genus Rhodococcus, and these tests are not suitable for accurate identification at the genus and species level. Among nucleic acid-based methods, the most powerful target gene for revealing reliable phylogenetic relationships is 16S ribosomal RNA gene (16S rRNA gene) sequence analysis, but this gene is unable to differentiation some of Rhodococcus species. To date, whole genome sequencing analysis has solved taxonomic complexities in this genus. Rhodococcus equi is the major cause of foal pneumonia, and its implication in human health is related to cases in immunocompromised patients. Macrolide family together with rifampicin is one of the most effective antibiotic agents for treatment rhodococcal infections.

Genome-Based Taxonomic Classification of the Phylum Actinobacteria

The application of phylogenetic taxonomic procedures led to improvements in the classification of bacteria assigned to the phylum Actinobacteria but even so there remains a need to further clarify relationships within a taxon that encompasses organisms of agricultural, biotechnological, clinical, and ecological importance. Classification of the morphologically diverse bacteria belonging to this large phylum based on a limited number of features has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees. Here, draft genome sequences of a large collection of actinobacterial type strains were used to infer phylogenetic trees from genome-scale data using principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families, and genera, as well as many species and a few subspecies were shown to be in need of revision leading to proposals for the recognition of 2 orders, 10 families, and 17 genera, as well as the transfer of over 100 species to other genera. In addition, emended descriptions are given for many species mainly involving the addition of data on genome size and DNA G+C content, the former can be considered to be a valuable taxonomic marker in actinobacterial systematics. Many of the incongruities detected when the results of the present study were compared with existing classifications had been recognized from 16S rRNA gene trees though whole-genome phylogenies proved to be much better resolved. The few significant incongruities found between 16S/23S rRNA and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences. Similarly good congruence was found between the discontinuous distribution of phenotypic properties and taxa delineated in the phylogenetic trees though diverse non-monophyletic taxa appeared to be based on the use of plesiomorphic character states as diagnostic features.

Diversity of culturable nocardioform actinomycetes from wastewater treatment plants in Spain and their role in the biodegradability of aromatic compounds

Currently, municipal and industrial wastewater treatment plants (WWTPs) are mainly focusing on reduction of biological oxygen demand and on the removal of nutrients. However, there are microorganisms that interfere with the process. In this environment, there is a large diversity of microorganisms that have not been studied in detail and that could provide real and practical solutions to the foaming problems. Among such microorganisms, Gram-positive actinomycete bacteria are of special interest because they are known for producing secondary metabolites as well as chemically diverse compounds and for their capacity to degrade recalcitrant pollutants. Three different media were chosen to isolate actinomycetes from 28 WWTPs in Spain. A total of 189 activated sludge samples were collected; 126 strains were isolated and identified to belong to 1 suborder, i.e. Corynebacterineae, and 7 genera, i.e. Corynebacterium, Dietzia, Gordonia, Mycobacterium, Rhodococcus, Tsukamurella and Williamsia. Furthermore, 71 strains were capable of biodegrading at least 1 aromatic product, and that 27 of them amplified for catA gene. The results of this research help us understand the complexity of the foam-forming microbial populations in Spain and it shows that WWTPs can be a good source of microorganisms that can degrade phenol or naphthalene.

Expression of Genes for a Flavin Adenine Dinucleotide-Binding Oxidoreductase and a Methyltransferase from Mycobacterium chlorophenolicum Is Necessary for Biosynthesis of 10-Methyl Stearic Acid from Oleic Acid in Escherichia coli

In living organisms, modified fatty acids are crucial for the functions of the cellular membranes and storage lipids where the fatty acids are esterified. Some bacteria produce a typical methyl-branched fatty acid, i.e., 10-methyl stearic acid (19:0Me10). The biosynthetic pathway of 19:0Me10 in vivo has not been demonstrated clearly yet. It had been speculated that 19:0Me10 is synthesized from oleic acid (18:1Δ9) by S-adenosyl-L-methionine-dependent methyltransfer and NADPH-dependent reduction via a methylenated intermediate, 10-methyelene octadecanoic acid. Although the recombinant methyltransferases UmaA and UfaA1 from Mycobacterium tuberculosis H₃₇Rv synthesize 19:0Me10 from 18:1Δ9 and NADPH in vitro, these methyltransferases do not possess any domains functioning in the redox reaction. These findings may contradict the two-step biosynthetic pathway. We focused on novel S-adenosyl-L-methionine-dependent methyltransferases from Mycobacterium chlorophenolicum that are involved in 19:0Me10 synthesis and selected two candidate proteins, WP_048471942 and WP_048472121, by a comparative genomic analysis. However, the heterologous expression of these candidate genes in Escherichia coli cells did not produce 19:0Me10. We found that one of the candidate genes, WP_048472121, was collocated with another gene, WP_048472120, that encodes a protein containing a domain associated with flavin adenine dinucleotide-binding oxidoreductase activity. The co-expression of these proteins (hereafter called BfaA and BfaB, respectively) led to the biosynthesis of 19:0Me10 in E. coli cells via the methylenated intermediate.

Degradation mechanisms of DDX induced by the addition of toluene and glycerol as cosubstrates in a zero-valent iron pretreated soil

Abiotic and biotic processes can be used to remediate DDX (DDT, DDD, DDE, and DDNS) contaminated soils; these processes can be fostered using specific carbon-amendments to stimulate particular soil indigenous microbial communities to improve rates or extent of degradation. In this study, toluene and glycerol were evaluated as cosubstrates under aerobic and anoxic conditions to determine the degradation efficiencies of DDX and to elucidate possible degradation mechanisms. Slurry microcosms experiments were performed during 60 days using pretreated soil with zero-valent iron (ZVI). Toluene addition enhanced the percentage of degradation of DDX. DDNS was the main compound degraded (around 86%) under aerobic conditions, suggesting cometabolic degradation of DDX by toluene-degrading soil bacteria. Glycerol addition under anoxic conditions favored the abiotic degradation of DDX mediated by sulfate-reducing bacteria activity, where DDT was the main compound degraded (around 90%). The 16S rDNA metagenomic analyses revealed Rhodococcus ruber and Desulfosporosinus auripigmenti as the predominant bacterial species after 40 days of treatment with toluene and glycerol additions, respectively. This study provides evidence of biotic and abiotic DDX degradation by the addition of toluene and glycerol as cosubstrates in ZVI pretreated DDX-contaminated soil.

Persistent organic pollutants induced protein expression and immunocrossreactivity by Stenotrophomonas maltophilia PM102: a prospective bioremediating candidate

A novel bacterium capable of growth on trichloroethylene as the sole carbon source was identified as Stenotrophomonas maltophilia PM102 by 16S rDNA sequencing (accession number of NCBI GenBank: JQ797560). In this paper, we report the growth pattern, TCE degradation, and total proteome of this bacterium in presence of various other carbon sources: toluene, phenol, glucose, chloroform, and benzene. TCE degradation was comparatively enhanced in presence of benzene. Densitometric analysis of the intracellular protein profile revealed four proteins of 78.6, 35.14, 26.2, and 20.47 kDa while the extracellular protein profile revealed two distinct bands at 14 kDa and 11 kDa that were induced by TCE, benzene, toluene, and chloroform but absent in the glucose lane. A rabbit was immunised with the total protein extracted from the bacteria grown in 0.2% TCE + 0.2% peptone. Antibody preadsorbed on proteins from peptone grown PM102 cells reacted with a single protein of 35.14 kDa (analysed by MALDI-TOF-mass-spectrometry) from TCE, benzene, toluene, or chloroform grown cells. No reaction was seen for proteins of PM102 grown with glucose. The PM102 strain was immobilised in calcium alginate beads, and TCE degradation by immobilised cells was almost double of that by free cells. The beads could be reused 8 times.

A membrane bioreactor for the simultaneous treatment of acetone, toluene, limonene and hexane at trace level concentrations

The performance of a flat-membrane biofilm reactor (MBR) for the removal of acetone, toluene, limonene and hexane at concentrations ranging from 1.3 to 3.2 mg m(-3) was investigated at different gas residence times (GRT): 60, 30, 15 and 7 s. A preliminary abiotic test was conducted to assess the mass transport of the selected volatile organic compounds (VOCs) through the membrane. A reduced transport of limonene and hexane was observed with water present over the dense side of the membrane. The presence of a biofilm attached on the dense side of the membrane following bioreactor inoculation significantly increased VOC transport. High acetone and toluene removals (>93%) were recorded in the MBR regardless of the GRT. To remediate the low hexane removal performance (RE < 24%) recorded at the initial stages of the process, a re-inoculation of the membrane with a hexane-degrading consortium embedded in silicon oil was performed. Although hexane removal did not exceed 27%, this re-inoculation increased limonene removals up to 90% at a GRT of 7 s. The absence of inhibition of hexane biodegradation by substrate competition confirmed that hexane removal in the MBR was indeed limited by the mass transfer through the membrane. Despite the low carbon source spectrum and load, the microbiological analysis of the communities present in the MBR showed high species richness (Shannon-Wiener indices of 3.2-3.5) and a high pair-wise similarity (84-97%) between the suspended and the attached biomass.

Isolation and characterization of a Rhodococcus strain with phenol-degrading ability and its potential use for tannery effluent biotreatment

INTRODUCTION

Wastewater derived from leather production may contain phenols, which are highly toxic, and their degradation could be possible through bioremediation technologies.

MATERIALS, METHODS AND RESULTS

In the present work, microbial degradation of phenol was studied using a tolerant bacterial strain, named CS1, isolated from tannery sediments. This strain was able to survive in the presence of phenol at concentrations of up to 1,000 mg/L. On the basis of morphological and biochemical properties, 16S rRNA gene sequencing, and phylogenetic analysis, the isolated strain was identified as Rhodococcus sp. Phenol removal was evaluated at a lab-scale in Erlenmeyer flasks and at a bioreactor scale in a stirred tank reactor. Rhodococcus sp. CS1 was able to completely remove phenol in a range of 200 to 1,000 mg/L in mineral medium at 30 ± 2 °C and pH 7 as optimal conditions. In the stirred tank bioreactor, we studied the effect of some parameters, such as agitation (200-600 rpm) and aeration (1-3 vvm), on growth and phenol removal efficiency. Faster phenol biodegradation was obtained in the bioreactor than in Erlenmeyer flasks, and maximum phenol removal was achieved at 400 rpm and 1 vvm in only 12 h. Furthermore, Rhodococcus sp. CS1 strain was able to grow and completely degrade phenols from tannery effluents after 9 h of incubation.

CONCLUSION

Based on these results, Rhodococcus sp. CS1 could be an appropriate microorganism for bioremediation of tannery effluents or other phenol-containing wastewaters.

Pseudonocardia hispaniensis sp. nov., a novel actinomycete isolated from industrial wastewater activated sludge

A novel actinomycete, designated PA3(T), was isolated from an oil refinery wastewater treatment plant, located in Palos de la Frontera, Huelva, Spain, and characterized taxonomically by using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate formed a distinct subclade in the Pseudonocardia tree together with Pseudonocardia asaccharolytica DSM 44247(T). The chemotaxonomic properties of the isolate, for example, the presence of MK-8 (H(4)) as the predominant menaquinone and iso-C(16:0) as the major fatty acid, are consistent with its classification in the genus Pseudonocardia. DNA:DNA pairing experiments between the isolate and the type strain of P. asaccharolytica DSM 44247(T) showed that they belonged to separate genomic species. The two strains were readily distinguished using a combination of phenotypic properties. Consequently, it is proposed that isolate PA3(T) represents a novel species for which the name Pseudonocardia hispaniensis sp. nov. is proposed. The type strain is PA3(T) (= CCM 8391(T) = CECT 8030(T)).

Molecular and infection biology of the horse pathogen Rhodococcus equi

The soil actinomycete Rhodococcus equi is a pulmonary pathogen of young horses and AIDS patients. As a facultative intracellular bacterium, R. equi survives and multiplies in macrophages and establishes its specific niche inside the host cell. Recent research into chromosomal virulence factors and into the role of virulence plasmids in infection and host tropism has presented novel aspects of R. equi infection biology and pathogenicity. This review will focus on new findings in R. equi biology, the trafficking of R. equi-containing vacuoles inside host cells, factors involved in virulence and host resistance and on host-pathogen interaction on organismal and cellular levels.

Biodegradation potential of the genus Rhodococcus

A large number of aromatic compounds and organic nitriles, the two groups of compounds covered in this review, are intermediates, products, by-products or waste products of the chemical and pharmaceutical industries, agriculture and the processing of fossil fuels. The majority of these synthetic substances (xenobiotics) are toxic and their release and accumulation in the environment pose a serious threat to living organisms. Bioremediation using various bacterial strains of the genus Rhodococcus has proved to be a promising option for the clean-up of polluted sites. The large genomes of rhodococci, their redundant and versatile catabolic pathways, their ability to uptake and metabolize hydrophobic compounds, to form biofilms, to persist in adverse conditions and the availability of recently developed tools for genetic engineering in rhodococci make them suitable industrial microorganisms for biotransformations and the biodegradation of many organic compounds. The peripheral and central catabolic pathways in rhodococci are characterized for each type of aromatics (hydrocarbons, phenols, halogenated, nitroaromatic, and heterocyclic compounds) in this review. Pathways involved in the hydrolysis of nitrile pollutants (aliphatic nitriles, benzonitrile analogues) and the corresponding enzymes (nitrilase, nitrile hydratase) are described in detail. Examples of regulatory mechanisms for the expression of the catabolic genes are given. The strains that efficiently degrade the compounds in question are highlighted and examples of their use in biodegradation processes are presented.

Microbial degradation of chlorinated benzenes

Chlorinated benzenes are important industrial intermediates and solvents. Their widespread use has resulted in broad distribution of these compounds in the environment. Chlorobenzenes (CBs) are subject to both aerobic and anaerobic metabolism. Under aerobic conditions, CBs with four or less chlorine groups are susceptible to oxidation by aerobic bacteria, including bacteria (Burkholderia, Pseudomonas, etc.) that grow on such compounds as the sole source of carbon and energy. Sound evidence for the mineralization of CBs has been provided based on stoichiometric release of chloride or mineralization of (14)C-labeled CBs to (14)CO(2). The degradative attack of CBs by these strains is initiated with dioxygenases eventually yielding chlorocatechols as intermediates in a pathway leading to CO(2) and chloride. Higher CBs are readily reductively dehalogenated to lower chlorinated benzenes in anaerobic environments. Halorespiring bacteria from the genus Dehalococcoides are implicated in this conversion. Lower chlorinated benzenes are less readily converted, and mono-chlorinated benzene is recalcitrant to biotransformation under anaerobic conditions.

Application of artificial neural network model for the development of optimized complex medium for phenol degradation using Pseudomonas pictorum (NICM 2074)

Biodegradation of phenol using Pseudomonas pictorum (NICM 2074) a potential biodegradant of phenol was investigated for its degrading potential under different operating conditions. The neural network input parameter set consisted of the same set of four levels of maltose (0.025, 0.05, 0.075 g/l), phosphate (3, 12.5, 22 g/l), pH (7, 8, 9) and temperature (30 degrees C, 32 degrees C, 34 degrees C) on phenol degradation was investigated and a Artificial Neural Network (ANN) model was developed to predict the extent of degradation. The learning, recall and generalization characteristic of neural networks was studied using phenol degradation system data. The efficiency of the model generated by the ANN, was tested and compared with the results obtained from an established second order polynomial multiple regression analysis (MRA). Further, the two models (ANN and MRA) were used to predict the percentage of degradation of phenol for blind test data. Performance of both the models were validated in the cases of training and test data, ANN was recommended based on the following higher coefficient of determination R (2); lower standard error of residuals and lower mean absolute percentage deviation.

Isolation and characterization of 1,2,4-trichlorobenzene mineralizing Bordetella sp. and its bioremediation potential in soil

A soil which has been polluted with chlorinated benzenes for more than 25 years was used for isolation of adapted microorganisms able to mineralize 1,2,4-trichlorobenzene (1,2,4-TCB). A microbial community was enriched from this soil and acclimated in liquid culture under aerobic conditions using 1,2,4-TCB as a sole available carbon source. From this community, two strains were isolated and identified by comparative sequence analysis of their 16S-rRNA coding genes as members of the genus Bordetella with Bordetella sp. QJ2-5 as the highest homological strain and with Bordetella petrii as the closest related described species. The 16S-rDNA of the two isolated strains showed a similarity of 100%. These strains were able to mineralize 1,2,4-TCB within two weeks to approximately 50% in liquid culture experiments. One of these strains was reinoculated to an agricultural soil with low native 1,2,4-TCB degradation capacity to investigate its bioremediation potential. The reinoculated strain kept its biodegradation capability: (14)C-labeled 1,2,4-TCB applied to this inoculated soil was mineralized to about 40% within one month of incubation. This indicates a possible application of the isolated Bordetella sp. for bioremediation of 1,2,4-TCB contaminated sites.

List of new names and new combinations previously effectively, but not validly, published

The purpose of this announcement is to effect the valid publication of the following new names and new combinations under the procedure described in theBacteriological Code(1990 Revision). Authors and other individuals wishing to have new names and/or combinations included in future lists should sendthree copies of the pertinent reprint or photocopies thereof to the IJSEM Editorial Officefor confirmation that all of the other requirements for valid publication have been met.It is also a requirement of IJSEM and the ICSP that authors of new species, new subspecies and new combinations provide evidence that types are deposited in two recognized culture collections in two different countries(i.e. documents certifying deposition and availability of type strains). It should be noted that the date of valid publication of these new names and combinations is the date of publication of this list, not the date of the original publication of the names and combinations. The authors of the new names and combinations are as given below, and these authors' names will be included in the author index of the present issue and in the volume author index. Inclusion of a name on these lists validates the publication of the name and thereby makes it available in bacteriological nomenclature. The inclusion of a name on this list is not to be construed as taxonomic acceptance of the taxon to which the name is applied. Indeed, some of these names may, in time, be shown to be synonyms, or the organisms may be transferred to another genus, thus necessitating the creation of a new combination.