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Applied Microbiology and Biotechnology (v.80, #1)

Production of phycocyanin—a pigment with applications in biology, biotechnology, foods and medicine by Niels T. Eriksen (pp. 1-14).

C-phycocyanin (C-PC) is a blue pigment in cyanobacteria, rhodophytes and cryptophytes with fluorescent and antioxidative properties. C-PC is presently extracted from open pond cultures of the cyanobacterium Arthrospira platensis although these cultures are not very productive and open for contaminating organisms. C-PC is considered a healthy ingredient in cyanobacterial-based foods and health foods while its colouring, fluorescent or antioxidant properties are utilised only to a minor extent. However, recent research and developments in C-PC synthesis and functionality have expanded the potential applications of C-PC in biotechnology, diagnostics, foods and medicine: The productivity of C-PC has been increased in heterotrophic, high cell density cultures of the rhodophyte Galdieria sulphuraria that are grown under well-controlled and axenic conditions. C-PC purification protocols based on various chromatographic principles or novel two-phase aqueous extraction methods have expanded in numbers and improved in performance. The functionality of C-PC as a fluorescent dye has been improved by chemical stabilisation of C-PC complexes, while protein engineering has also introduced increased stability and novel biospecific binding sites into C-PC fusion proteins. Finally, our understanding of the physiological functions of C-PC in humans has been improved by a mechanistic hypothesis that links the chemical properties of the phycocyanobilin chromophores of C-PC to the natural antioxidant, bilirubin, and may explain the observed health benefits of C-PC intake. This review outlines how C-PC is produced and utilised and discusses the novel C-PC synthesis procedures and applications.

Keywords: Arthrospira platensis ; Galdieria sulphuraria ; Heterotrophic; Nutraceutical; Photoautotrophic; Recombinant

Aranciamycin analogs generated by combinatorial biosynthesis show improved antitumor activity by Andriy Luzhetskyy; Jens Hoffmann; Stefan Pelzer; Sven-Eric Wohlert; Andreas Vente; Andreas Bechthold (pp. 15-19).

Expression of the aranciamycin biosynthetic gene cluster in Streptomyces diastatochromogenes Tü6028 resulted in production of four novel compounds, aranciamycins E, F, G, and H with different decorations in the tetracyclic backbone. Two derivatives contain a d-amicetose moiety at C₇ (aranciamycins F and G), two are hydroxylated at position C₁ (aranciamycins E and G), and one is hydroxylated at C₁₃ (aranciamycin F). Analysis of the biological activities of the aranciamycins against two human tumor cell lines—MCF-7 and MATU—shows surprising impact of the hydroxyl group at position C₁ on activity. As aranciamycins E and G were the most active derivatives, hydroxylation of the C₁ appears to coincide with increased antitumor activity of aranciamycins.

Keywords: Aranciamycin; Anthracyclines; Combinatorial biosynthesis; Anticancer activity

Optimization of culture conditions and scale-up to plant scales for teicoplanin production by Actinoplanes teichomyceticus by Hyung-Moo Jung; Sang-Yong Kim; Ponnandy Prabhu; Hee-Jung Moon; In-Won Kim; Jung-Kul Lee (pp. 21-27).

This report describes the optimization of culture conditions for teicoplanin production by Actinoplanes teichomyceticus KCCM-10601, an identified high-teicoplanin-producing strain (US 2006/0134757 A1). Among the conditions tested, temperature, pH, and the dissolved oxygen tension (DOT) were key factors affecting teicoplanin production. When the temperature, pH, and DOT were controlled at 34 °C, 7.0 and 20–30%, respectively, a dry-cell weight of 42.8 g l⁻¹ and a teicoplanin production of 2.9 g l⁻¹ were obtained after 120 h of batch culture, corresponding to a specific teicoplanin content of 67.8 mg g-DCW⁻¹. Teicoplanin production was scaled-up from a laboratory scale (7-l fermenter) to a pilot scale (300 l) and a plant scale (5,000 l) using the impeller tip velocity (V _tip) as a scale-up parameter. Teicoplanin production at the laboratory scale was similar to those at the pilot and plant scales. This is the highest report of pilot- and plant-scale production of teicoplanin.

Keywords: Actinoplanes teichomyceticus ; DOT; Impeller tip velocity; Optimization; Scale-up; Teicoplanin

Preparation of lipophilic alkyl (hydroxy)benzoates by solvent-free lipase-catalyzed esterification and transesterification by K. Vosmann; B. Wiege; P. Weitkamp; N. Weber (pp. 29-36).

Long-chain alkyl benzoates, e.g., lauryl 4-hydroxybenzoate, palmityl 4-hydroxybenzoate, and oleyl 4-hydroxy-3-methoxybenzoate, are formed in high to moderate conversion by lipase-catalyzed transesterification of the corresponding short-chain alkyl benzoates (0.3 to 1 mmol) with fatty alcohols in an equimolar ratio. The substrates are reacted in vacuo in the absence of solvents and drying agents in the reaction mixture. Immobilized lipase B from Candida antarctica (Novozym 435) demonstrates higher activity for the transesterification of various methyl (hydroxy)benzoates with long-chain alcohols than for the corresponding esterification reactions. For example, transesterification activity is around 25-fold higher than esterification activity for the preparation of oleyl 4-hydroxybenzoate. The relative transesterification activities of methoxy- and hydroxy-substituted methyl benzoates found for Novozym 435 are as follows: 2-methoxybenzoate ≈ 3-methoxybenzoate > 4-methoxybenzoate > 3-hydroxybenzoate ≈ 2-hydroxybenzoate > 4-hydroxybenzoate ≈ 4-hydroxy-3-methoxybenzoate ≈ 3-hydroxy-4-methoxybenzoate > > 3,4-dihydroxybenzoate. With respect to the position of the substituents at the phenyl moiety of methyl benzoates, transesterification activity of Novozym 435 increases in the order ortho ≈ meta > para. Compounds with inverse chemical structure, e.g., (methoxy)benzyl alkanoates, are formed in much higher rates both by esterification and transesterification than the analogous alkyl benzoates. Purification by deacidification, crystallization, or vacuum distillation yielded 74% to 89% of the reaction products.

Keywords: Oleyl 4-hydroxybenzoate; Oleyl 4-hydroxy-3-methoxybenzoate (Oleyl vanillate); 3-Hydroxybenzyl oleate; Immobilized lipase B from Candida antarctica (Novozym 435); Esterification; Transesterification

Furanone derivatives as quorum-sensing antagonists of Pseudomonas aeruginosa by Cheoljin Kim; Jaeeun Kim; Hyung-Yeon Park; Hee-Jin Park; Joon Hee Lee; Chan Kyung Kim; Jeyong Yoon (pp. 37-47).

The biofilm formation of Pseudomonas aeruginosa, an opportunistic human pathogen, is developed by cell-to-cell signaling, so-called quorum sensing (QS). To control the biofilm formation, we designed and synthesized new QS inhibitors of P. aeruginosa based on the structure of the previously known QS inhibitor, furanone. Newly synthesized compounds were a series of analogs of (5-oxo-2,5-dihydrofuran-3-yl)methyl alkanoate, and the structures of all six synthesized compounds was confirmed by NMR and GC/MS analyses. These new QS inhibitor candidates could remarkably inhibit both Pseudomonas QS signaling and biofilm formation, which were assayed by using the recombinant reporter system and flow cell confocal microscopy. The degree of QS inhibition by these new inhibitors varied from 20% to 90%. For the profound understanding about inhibition mechanism, we tried to estimate the binding energy between QS receptor, LasR, and our inhibitors from the in silico modeling system. The predicted binding pattern from the modeling system and our experimental data about QS inhibition were in good agreement. From these results, we suggest a new approach to develop the QS inhibitors and biofilm control agents based on structural modeling.

Keywords: Quorum-sensing inhibitors; Cell-to-cell communication; Furanone derivatives; FlexX docking; Binding energies (docking score)

Immobilization–stabilization of a new recombinant glutamate dehydrogenase from Thermus thermophilus by Juan M. Bolivar; Felipe Cava; Cesar Mateo; Javier Rocha-Martín; Jose M. Guisán; José Berenguer; Roberto Fernandez-Lafuente (pp. 49-58).

The genome of Thermus thermophilus contains two genes encoding putative glutamate dehydrogenases. One of these genes (TTC1211) was cloned and overexpressed in Escherichia coli. The purified enzyme was a trimer that catalyzed the oxidation of glutamate to α-ketoglutarate and ammonia with either NAD⁺ or NADP⁺ as cofactors. The enzyme was also able to catalyze the inverse reductive reaction. The thermostability of the enzyme at neutral pH was very high even at 70°C, but at acidic pH values, the dissociation of enzyme subunits produced the rapid enzyme inactivation even at 25°C. The immobilization of the enzyme on glyoxyl agarose permitted to greatly increase the enzyme stability under all conditions studied. It was found that the multimeric structure of the enzyme was stabilized by the immobilization (enzyme subunits could be not desorbed from the support by boiling it in the presence of sodium dodecyl sulfate). This makes the enzyme very stable at pH 4 (e.g., the enzyme activity did not decrease after 12 h at 45°C) and even improved the enzyme stability at neutral pH values. This immobilized enzyme can be of great interest as a biosensor or as a biocatalyst to regenerate both reduced and oxidized cofactors.

Keywords: Redox enzymes; Thermophilic enzymes hyperstabilization; Multipoint immobilization; Multimeric enzyme stabilization; Cofactor regeneration; Glutamate biosensor

Purification and characterization of Chromobacterium sp. DS-1 cholesterol oxidase with thermal, organic solvent, and detergent tolerance by Noriyuki Doukyu; Kanpei Shibata; Hiroyasu Ogino; Martin Sagermann (pp. 59-70).

A new screening method for 6β-hydroperoxycholest-4-en-3-one (HCEO)-forming cholesterol oxidase was devised in this study. As the result of the screening, a novel cholesterol oxidase producer (strain DS-1) was isolated and identified as Chromobacterium sp. Extracellular cholesterol oxidase of strain DS-1 was purified from the culture supernatant. The molecular mass of the purified enzyme was 58 kDa. This enzyme showed a visible adsorption spectrum having peaks at 355 and 450 nm, like a typical flavoprotein. The enzyme oxidized cholesterol to HCEO, with the consumption of 2 mol of O₂ and the formation of 1 mol of H₂O₂ for every 1 mol of cholesterol oxidized. The enzyme oxidized 3β-hydroxysteroids such as cholesterol, β-cholestanol, and pregnenolone at high rates. The K _m value for cholesterol was 26 μM. The enzyme was stable at pH 3 to 11 and most active at pH 7.0–7.5, showing optimal activity at pH 7.0 and 65°C. The enzyme retained about 80% of its activity after incubation for 30 min at 85°C. The thermal stability of the enzyme was the highest among the cholesterol oxidases tested. Moreover, the enzyme was more stable in the presence of various organic solvents and detergents than commercially available cholesterol oxidases.

Keywords: Cholesterol oxidase; Chromobacterium; Protein purification; Organic solvent; Detergent; Thermal stability

Purification and characterization of thermostable H₂O₂-forming NADH oxidase from 2-phenylethanol-assimilating Brevibacterium sp. KU1309 by Jun-ichiro Hirano; Kenji Miyamoto; Hiromichi Ohta (pp. 71-78).

A cytoplasmic NADH oxidase (NOX) was purified from a soil bacteria, Brevibacterium sp. KU1309, which is able to grow in the medium containing 2-phenylethanol as the sole source of carbon under an aerobic condition. The enzyme catalyzed the oxidation of NADH to NAD⁺ involving two-electron reduction of O₂ to H₂O₂. The molecular weight of the enzyme was estimated to be 102 kDa by gel filtration and 57 kDa by SDS-PAGE, which indicates that the NOX was a homodimer consisting of a single subunit. The enzyme was stable up to 70°C at a broad range of pH from 7 to 11. The enzyme activity increased about ten-fold with the addition of ammonium salt, while it was inhibited by Zn²⁺ (39%), Cu²⁺ (41%), Hg²⁺ (72%) and Ag⁺ (37%). The enzyme acts on NADH, but not on NADPH. The regeneration of NAD⁺ utilizing this enzyme made selective oxidation of mandelic acid or l-phenylalanine possible. This thermostable enzyme is expected to be applicable as a useful biocatalyst for NAD⁺ recycling.

Keywords: NADH oxidase; Brevibacterium sp.; Cofactor regeneration; Molecular oxygen; Hydrogen peroxide

Genetic modification of Lactobacillus plantarum by heterologous gene integration in a not functional region of the chromosome by Franca Rossi; Alessandro Capodaglio; Franco Dellaglio (pp. 79-86).

This report describes the vector-free engineering of Lactobacillus plantarum by chromosomal integration of an exogenous gene without inactivation of physiological traits. The integrative plasmid vector pP7B6 was derived from pGIP73 by replacing the cbh site, encoding the L. plantarum conjugated bile salt hydrolase, with the prophage fragment P7B6, from L. plantarum Lp80 (DSM 4229). Plasmid pP7B6NI was obtained by inserting the nisin immunity gene nisI of Lactococcus lactis subsp. lactis DSM 20729, preceded by the constitutive promoter P32 from the same strain, in a unique XbaI site of fragment P7B6 and was used to electrotransform L. plantarum Lp80. A food grade recombinant L. plantarum Lp80NI, with 480-fold higher immunity to nisin than the wild type, was derived by integration of pP7B6NI followed by the excision of pP7B6. Polymerase chain reaction tests demonstrated that the integration of nisI in the prophage region had occurred and that the erythromycin resistance marker from pP7B6 was lost. Fifteen among 31 L. plantarum strains tested hybridized with P7B6, indicating that the integration of pP7B6-derived vectors might occur in some other L. plantarum strains. This was experimentally confirmed by constructing the recombinant strain L. plantarum LZNI from the dairy isolate L. plantarum LZ (LMG 24600).

Keywords: Lactobacillus plantarum ; Food grade genetic engineering; Chromosomal integration of a foreign gene; Prophage genes

Simultaneous expression of an arylacetonitrilase from Pseudomonas fluorescens and a (S)-oxynitrilase from Manihot esculenta in Pichia pastoris for the synthesis of (S)-mandelic acid by Sven Rustler; Hassan Motejadded; Josef Altenbuchner; Andreas Stolz (pp. 87-97).

The arylacetonitrilase of Pseudomonas fluorescens EBC191 catalyzes the conversion of (S)-mandelonitrile to (S)-mandelic acid and (S)-mandeloamide. This biotransformation is optimally performed under acidic pH values because (S)-mandelonitrile rapidly decomposes under neutral conditions. Therefore, the gene encoding the arylacetonitrilase of P. fluorescens EBC191 was integrated and expressed under the control of the AOX1 promoter in the methylotrophic yeast Pichia pastoris which was supposed to act as an acidotolerant expression system. These recombinant strains hydrolyzed (R,S)-mandelonitrile at pH values ≥3 to mandelic acid and mandeloamide and were more acidotolerant than previously constructed Escherichia coli whole cell catalysts synthesizing the same nitrilase activity. Subsequently, recombinant P. pastoris strains were constructed which simultaneously expressed the (S)-oxynitrilase of Manihot esculenta and the arylacetonitrilase of P. fluorescens EBC191 each under the control of individual AOX1 promoters in order to obtain a whole cell catalyst for the synthesis of (S)-mandelic acid from benzaldehyde and cyanide. Resting cells of the recombinant strains converted under acidic conditions benzaldehyde and cyanide initially to mandelonitrile which was immediately converted to mandelic acid and mandeloamide. The chiral analysis of the products formed revealed a high enantiomeric excess for the (S)-enantiomers.

Keywords: Nitrilase; Oxynitrilase; Biotransformation; Acidotolerance; (S)-mandelic acid; Manihot esculenta ; Pseudomonas fluorescens ; Pichia pastoris

Real-time quantitative analysis of carbon catabolite derepression of cellulolytic genes expressed in the basidiomycete Phanerochaete chrysosporium by Hitoshi Suzuki; Kiyohiko Igarashi; Masahiro Samejima (pp. 99-106).

Production of cellulolytic enzymes, such as cellobiohydrolases (CBH) and cellobiose dehydrogenase (CDH), by the basidiomycete Phanerochaete chrysosporium is significantly repressed in glucose-containing media; this is known as carbon catabolite repression. We have analyzed the glucose concentration dependence of transcript numbers of the cellulolytic genes (cel6A, cel7D, and cdh) and β-glucosidase gene (bgl3A) by means of real-time quantitative reverse transcriptase polymerase chain reaction to investigate the roll of carbon catabolite derepression in these gene expression. When the mycelium of P. chrysosporium grown in glucose culture was transferred to media containing various concentrations of glucose (0–5,000 μM), the expression levels of cel6A, cel7D, and cdh were drastically influenced by glucose, whereas no significant change was observed in bgl3A. The numbers of transcripts of cel6A, cel7D, and cdh increased exponentially during incubation for 6 h in the culture without glucose, and the rates of increase were 2.1 times per hour for cel6A transcripts and 2.7 times per hour for cel7D transcripts. Moreover, derepression of cel6A and cel7D was delayed (by 1.6 and 0.6 h, respectively) when the culture contained 50 μM glucose compared with that in the absence of glucose, suggesting that the promoter activities of cel7D and cel6A are distinct under conditions of carbon catabolite derepression.

Keywords: Carbon catabolite derepression; Phanerochaete chrysosporium ; Cellulose degradation; Real-time PCR

Effect of the osmotic conditions during sporulation on the subsequent resistance of bacterial spores by Hue Nguyen Thi Minh; Jean-Marie Perrier-Cornet; Patrick Gervais (pp. 107-114).

The causes of Bacillus spore resistance remain unclear. Many structures including a highly compact envelope, low hydration of the protoplast, high concentrations of Ca-chelated dipicolinic acid, and the presence of small acid-soluble spore proteins seem to contribute to resistance. To evaluate the role of internal protoplast composition and hydration, spores of Bacillus subtilis were produced at different osmotic pressures corresponding to water activities of 0.993 (standard), 0.970, and 0.950, using the two depressors (glycerol or NaCl). Sporulation of Bacillus subtilis was slower and reduced in quantity when the water activity was low, taking 4, 10, and 17 days for 0.993, 0.970, and 0.950 water activity, respectively. The spores produced at lower water activity were smaller and could germinate on agar medium at lower water activity than on standard spores. They were also more sensitive to heat (97 °C for 5–60 min) than the standard spores but their resistance to high hydrostatic pressure (350 MPa at 40 °C for 20 min to 4 h) was not altered. Our results showed that the water activity of the sporulation medium significantly affects spore properties including size, germination capacity, and resistance to heat but has no role in bacterial spore resistance to high hydrostatic pressure.

Keywords: Bacterial spores; Bacillus subtilis ; Water activity; Heat; High hydrostatic pressure

Isolation and partial characterization of Bacillus subtilis ME488 for suppression of soilborne pathogens of cucumber and pepper by Soohee Chung; Hyesuk Kong; Jeffrey S. Buyer; Dilip K. Lakshman; John Lydon; Sang-Dal Kim; Daniel P. Roberts (pp. 115-123).

Environmentally friendly control measures are needed for suppression of soilborne pathogens of vegetable crops in the Republic of Korea. In vitro challenge assays were used to screen approximately 500 bacterial isolates from 20 Korean greenhouse soils for inhibition of diverse plant pathogens. One isolate, Bacillus subtilis ME488, suppressed the growth of 39 of 42 plant pathogens tested. Isolate ME488 also suppressed the disease caused by Fusarium oxysporum f. sp. cucumerinum on cucumber and Phytophthora capsici on pepper in pot assays. Polymerase chain reaction was used to screen isolate ME488 for genes involved in biosynthesis of 11 antibiotics produced by various isolates of B. subtilis. Amplicons of the expected sizes were detected for bacD and bacAB, ituC and ituD, and mrsA and mrsM involved in the biosynthesis of bacilysin, iturin, and mersacidin, respectively. The identity of these genes was confirmed by DNA sequence analysis of the amplicons. Bacilysin and iturin were detected in culture filtrates from isolate ME488 by gas chromatography coupled with mass spectroscopy and by thin layer chromatography, respectively. Detection of mersacidin in ME488 culture filtrates was not attempted. Experiments reported here indicate that B. subtilis ME488 has potential for biological control of pathogens of cucumber and pepper possibly due to the production of antibiotics.

Keywords: Bacillus subtilis ; Bacilysin; Biological control; Fusarium oxysporum f. sp. cucumerinum ; Iturin; Mersacidin; Methyl bromide replacement; Phytophthora capsici

Determination of fungal activity in modified wood by means of micro-calorimetry and determination of total esterase activity by Pradeep Verma; Jens Dyckmans; Holger Militz; Carsten Mai (pp. 125-133).

Beech and pine wood blocks were treated with 1,3-dimethylol-4,5-dihydroxyethylen urea (DMDHEU) to increasing weight percent gains (WPG). The resistance of the treated specimens against Trametes versicolor and Coniophora puteana, determined as mass loss, increased with increasing WPG of DMDHEU. Metabolic activity of the fungi in the wood blocks was assessed as total esterase activity (TEA) based on the hydrolysis of fluorescein diacetate and as heat or energy production determined by isothermal micro-calorimetry. Both methods revealed that the fungal activity was related with the WPG and the mass loss caused by the fungi. Still, fungal activity was detected even in wood blocks of the highest WPG and showed that the treatment was not toxic to the fungi. Energy production showed a higher consistency with the mass loss after decay than TEA; higher mass loss was more stringently reflected by higher heat production rate. Heat production did not proceed linearly, possibly due to the inhibition of fungal activity by an excess of carbon dioxide.

Keywords: Brown rot; Fungal activity; Micro-calorimetry; Total esterase activity; White rot; Wood modification

Effect of monensin feeding and withdrawal on populations of individual bacterial species in the rumen of lactating dairy cows fed high-starch rations by Paul J. Weimer; David M. Stevenson; David R. Mertens; Elvin E. Thomas (pp. 135-145).

Real-time polymerase chain reaction (PCR) was used to quantify 16 procaryotic taxa in the rumina of two lactating dairy cows following supply and subsequent withdrawal of the feed additive monensin (13.9 mg/kg of diet dry matter) in a high-starch, silage-based ration. PCR was conducted on DNA from rumen samples collected 6 h post feeding on two successive days before monensin supplementation, after 30 days of monensin supplementation, and at six weekly intervals after monensin withdrawal. Mean values of relative population size (RPS, the percent of bacterial 16S rRNA copy number) for genus Prevotella increased (P < 0.05) from 41.8% without monensin to 49.2% with monensin and declined to 42.5% after monensin withdrawal. Mean RPS values for two biohydrogenating species (Megasphaera elsdenii and Butyrivibrio fibrisolvens) were low (<0.4%) and declined several-fold in response to monensin. Mean RPS values for the biohydrogenating species Eubacterium ruminantium, four cellulolytic species, four starch- or dextrin-fermenting species, and Domain Archaea were not altered (P > 0.10) upon monensin feeding or withdrawal. The data suggest that monensin in high-starch diets does not suppress populations of classical ruminal Gram-positive bacteria or the availability of H₂, though it may affect bacteria involved in biohydrogenation of lipids that regulate bovine mammary lipogenesis.

Keywords: Rumen; Real-time PCR; Bacterial populations; Dairy cattle; Prevotella ; Biohydrogenation

Toluene gas phase biofiltration by Paecilomyces lilacinus and isolation and identification of a hydrophobin protein produced thereof by Gabriel Vigueras; Keiko Shirai; Daniel Martins; Telma Teixeira Franco; Luciana Francisco Fleuri; Sergio Revah (pp. 147-154).

Paecilomyces lilacinus consumed toluene as the sole carbon source in a gas-phase biofilter packed with perlite obtaining an average elimination capacity of 50 g m⁻³ h⁻¹, a removal efficiency of 53%, and a final biomass of 31.6 mg biomass g dry support⁻¹. Hydrophobin proteins from the mycelium produced in the biofilter were purified by formic acid extraction and precipitated by electrobubbling, and the molecular weight was found to be 10.6 ± 0.3 kDa. The peptide mass fingerprinting analysis of the purified hydrophobin by matrix-assisted laser desorption/ionization time-of-flight resulted in the identification of two peptides that presented high homology with sequences of class I hydrophobin proteins from other ascomycetous fungi when compared against the National Center for Biotechnology Information database. The yield of hydrophobin (PLHYD) from P. lilacinus was 1.1 mg PLHYD g biomass⁻¹. These proteins modified the hydrophobicity of Teflon by lowering the contact angle from 130.1 (±2)° to 57.0 (±5)° supporting hot sodium dodecyl sulfate washing. This work is the first report about biodegradation of toluene by the nematophagous fungus P. lilacinus in a gas-phase biofilter and the identification of its hydrophobin protein.

Keywords: Fungal biofilter; Paecilomyces lilacinus ; Hydrophobicity; Hydrophobins

The ars genotype characterization of arsenic-resistant bacteria from arsenic-contaminated gold–silver mines in the Republic of Korea by Jin-Soo Chang; Yang-Hoon Kim; Kyoung-Woong Kim (pp. 155-165).

The isolates were identified on the basis of ars genotype characteristics as well as arsenic oxidation/reduction analysis based on the molecular detection characterization. Diversity, pH range (4.0 to 7.0), location, and ars features were assessed for four arsenic-contaminated pond sites and six arsenic tailings located in the Duck-um mine and Myoung-bong mine areas. The presence of ars genes in the genomes of each bacterial strain was evaluated using polymerase chain reaction. Batch experiment results showed that Pseudomonas putida strains OS-3 and -18 completely oxidized 1 mM of arsenite(III) to arsenate(V) within 35–40 h. In contrast, two arsenate-reducing bacteria isolated from mines, P. putida RS-4 and RS-5, were capable of growing aerobically in growth medium supplemented with up to 66.7 mM arsenate(V), which are significantly higher concentration than those tolerated by other arsenic-resistant bacteria. These results suggest that newly isolated indigenous arsenic-resistant bacteria may provide a better understanding of the molecular geomicrobiology and may be applied to the bioremediation of arsenic-contaminated mines in Korea. Ecologically, the redox potential plays an important role in arsenic toxicity and mobility in As-contaminated mine areas, as it facilitates the biogeochemical cycling activity of Pseudomonas sp. groups.

Keywords: Arsenic-resistant bacteria; Arsenic resistance system (ars); ars genotype; Arsenic-contaminated abandoned mine

Biocontrol potential and polyphasic characterization of novel native Trichoderma strains against Macrophomina phaseolina isolated from sorghum and common bean by C. P. Larralde-Corona; M. R. Santiago-Mena; A. M. Sifuentes-Rincón; I. C. Rodríguez-Luna; M. A. Rodríguez-Pérez; K. Shirai; J. A. Narváez-Zapata (pp. 167-177).

Native strains of Trichoderma isolated from sorghum and common bean crop soils were investigated to assess their biocontrol potential over the phytopathogenic fungus Macrophomina phaseolina, isolated from diseased plants. The Trichoderma strains were characterized with a polyphasic approach, which combined the analysis of their morphological characteristics, enzymatic activity, macro- and microculture test results, rDNA restriction patterns (AFLP), ITS1–5.8S–ITS2 rDNA sequences, and protein profiles. The integration of these data sets can be used to select new isolates as biological control agents against native fungal phytopathogens. In general, we observed a positive correlation between the secretion of β-1,3-glucanase and N-acetylhexosaminidase, and the biocontrol capacities of all the Trichoderma isolates. Strains with the best hyperparasitic behavior against M. phaseolina isolated from diseased bean and sorghum were Trichoderma sp. (TCBG-2) and Trichoderma koningiopsis (TCBG-8), respectively.

Keywords: Biocontrol; Trichoderma isolates; Macrophomina phaseolina ; Polyphasic characterization

Toluene gas phase biofiltration by Paecilomyces lilacinus and isolation and identification of a hydrophobin protein produced thereof by Gabriel Vigueras; Keiko Shirai; Daniel Martins de Souza; Telma Teixeira Franco; Luciana Francisco Fleuri; Sergio Revah (pp. 179-179).

Effect of the osmotic conditions during sporulation on the subsequent resistance of bacterial spores by Hue Nguyen Thi Minh; Stéphane Guyot; Jean-Marie Perrier-Cornet; Patrick Gervais (pp. 181-181).

ErratumTo: Effect of the osmotic conditions during sporulation on the subsequent resistance of bacterial spores by Hue Nguyen Thi Minh; Stéphane Guyot; Jean-Marie Perrier-Cornet; Patrick Gervais (pp. 181-181).

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Applied Microbiology and Biotechnology (v.80, #1)

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Applied Microbiology and Biotechnology (v.80, #1)