Bacillus Firmus Research Articles

Decolorization and partial mineralization of a polyazo dye by Bacillus firmus immobilized within tubular polymeric gel

The degradation of C.I. Direct red 80, a polyazo dye, was investigated using Bacillus firmus immobilized by entrapment in tubular polymeric gel. This bacterial strain was able to completely decolorize 50 mg/L of C.I. Direct red 80 under anoxic conditions within 12 h and also degrade the reaction intermediates (aromatic amines) during the subsequent 12 h under aerobic conditions. The tubular gel harboring the immobilized cells consisted of anoxic and aerobic regions integrated in a single unit which was ideal for azo dye degradation studies. Results obtained show that effective dye decolorization (97.8%), chemical oxygen demand (COD) reduction (91.7%) and total aromatic amines removal were obtained in 15 h with the immobilized bacterial cell system whereas for the free cells, a hydraulic residence time of 24 h was required for an equivalent performance in a sequential anoxic and aerobic process. Repeated-batch experiments indicate the immobilized cells could decolorize C.I. Direct red 80 and reduce medium COD in five successive batch runs with enhanced activity obtained after each consecutive run, thus suggesting its stability and potential for repeated use in wastewater treatment. UV–visible spectrophotometry and HPLC analysis were used to confirm the partial mineralization of the dye. Data from this study could be used as a reference for the development of effective industrial scale biotechnological process for the removal of dyes and their metabolites in textile wastewater.

Asphaltene biodegradation using microorganisms isolated from oil samples

Twenty-five species were isolated from oil and polluted soil samples of Dorood oilfield, in the south of Iran, which were able to utilize asphaltene as a sole carbon and energy sources. Isolated microorganisms, in the form of pure and mixed, were cultured for 2 months at 28°C in a medium containing asphaltene. Five of the isolated microorganisms which higher growth on asphaltene were identified as Pseudomonas spp TMU2-5, Bacillus licheniformis TMU1-1, Bacillus lentus TMU5-2, Bacillus cereus TMU8-2, and Bacillus firmus TMU6-2. These bacteria degrade 40–46% of asphaltene and among them B. lentus TMU5-2 showed the greatest capability for degradation asphaltene. Biodegradation of asphaltene by the mixed culture of five bacteria was 48%, this is the highest reported degradation result. The bacterial mixed culture growth, in a bubble-column (55×7.5cm), was evaluated by CHN and FTIR analysis during 2 months of incubation. The values of pH, salinity and asphaltene concentration for degradation at 40°C were optimized by response surface methodology for pure cultures of B. lentus and the optimum results are 6.7, 76gL−1 and 22gL−1, respectively, and for the mixed culture as 6.4, 76gL−1 and 12gL−1, respectively. Conducted kinetic study showed that the data of asphaltene biodegradation fit to Tessier model and the growth kinetic parameter were obtained as μmax=0.31day−1, ks=39.19gL−1 and Yxs=0.21.

Evaluation of colour removal in synthetic saline wastewater containing azo dyes using an immobilized halotolerant cell system

Studies were carried out to evaluate the colour removal capacity of a moderately halotolerant bacterium, Bacillus firmus, in synthetic saline wastewater medium (SSWM) under static condition. The bacterial strain effectively decolourized Polar red B (an azo dye) in a wide range of sodium chloride (1–6%, w/v), dye (5–100 mg/L) and SDS (0.1–5.0 mg/L) concentrations and at pH range of 6–10 after 24 h of incubation. Cell immobilization studies indicated that colour removal was significantly higher ( p < 0.05) in immobilized halotolerant cell systems than with free cells of B. firmus especially at salt concentrations higher than 4%. Results suggest the potential of using the immobilized halotolerant cell system for effective treatment of dye-contaminated saline wastewaters.

Optimisation of process parameters for bioreduction of azo dyes using Bacillus firmus under batch anaerobic condition

A new dye decolourising bacterial strain was isolated from textile wastewater and identified as Bacillus firmus. The study indicated that the bacterium could efficiently decolourise different azo dyes under static culture conditions. Characterisation of the efficiency of azo dye reduction by this isolate using both spectral and HPLC analysis was found to be a function of process parameters which include dye concentration, culture broth pH, incubation temperature, aeration as well as nitrogen source. For decolourisation, the optimal pH and temperature were 7–8 and 20–35°C respectively, while remarkable dye degradation was obtained within 18 h for dye concentrations below 100 mg L−1. With the addition of yeast extract and under optimal conditions, dye reduction was enhanced and complete colour removal was achieved within 12 h. Colour removal was shown to be due to biodegradation rather than adsorption of dyes on bacterial cells. This study confirms the ability of the new dye‐degrading strain, Bacillus firmus, to decolourise and degrade different azo dyes and highlights its high biotechnology potential for the eco‐friendly treatment of textile wastewater when optimal conditions are applied.

English

&nbsp; Thermostable alkaline&nbsp;&alpha;-amylase producing bacterium&nbsp;Bacillus&nbsp;firmus&nbsp;CAS 7&nbsp;strain isolated from marine sediment of Parangipettai coast grew maximally in both shake flasks. Potato peel was found to be a superior substrate for the production of &alpha;-amylase at 35&deg;C, pH 7.5 and 1.0% of substrate concentrations. Under optimal conditions,&nbsp;B. firmus&nbsp;produced&nbsp;676&nbsp;U/ml of &alpha;-amylase which was optimally active at 50&deg;C and pH 9.0. &nbsp; Key words:&nbsp;&alpha;-Amylase, potato peel substrate,&nbsp;Bacillus&nbsp;firmus&nbsp;CAS 7, thermostable, marine.

Accumulation of Polyhydroxyalkanoates by Rhizobacteria Underneath Nickel-Hyperaccumulators from Serpentine Ecosystem

Nickel-resistant bacteria isolated from underneath Ni-hyperaccumulators growing on serpentine soils were screened for production of polyhydroxyalkanoates. These rhizobacteria accumulated poly-3-hydroxybutyric acid [P(3HB)] accounting 3.9–67.7% of cell dry weight during growth in gluconate and/or glucose. Cupriavidus pauculus KPS 201 utilized only gluconate and accumulated about 67.7% P(3HB) while, Bacillus firmus AND 408 utilized both carbon sources for polymer synthesis. The isolates being resistant to Ni also accumulated substantial amount of P(3HB) when grown in presence of the heavy metal and this was revealed by transmission electron microscopic studies. Although B. firmus AND 408 produced only P(3HB) at higher concentrations of gluconate, C. pauculus KPS 201 synthesized copolymer of 3-hydroxybutyric acid (3HB) and 3-hydroxyvaleric acid (3HV) [P(3HB-co-3HV)]. In presence of 0.8% gluconate and 4 mM Ni, KPS 201 cells produced PHA amounting 81% CDW, which contained 76 and 24 mol% 3HB and 3HV monomers, respectively.

Bacillus purgationiresistans sp. nov., isolated from a drinking-water treatment plant

A Gram-positive, aerobic, non-motile, endospore-forming rod, designated DS22(T), was isolated from a drinking-water treatment plant. Cells were catalase- and oxidase-positive. Growth occurred at 15-37 °C, at pH 7-10 and with <8% (w/v) NaCl (optimum growth: 30 °C, pH 7-8 and 1-3% NaCl). The major respiratory quinone was menaquinone 7, the G+C content of the genomic DNA was 36.5 mol% and the cell wall contained meso-diaminopimelic acid. On the basis of 16S rRNA gene sequence analysis, strain DS22(T) was a member of the genus Bacillus. Its closest phylogenetic neighbours were Bacillus horneckiae NRRL B-59162(T) (98.5% 16S rRNA gene sequence similarity), Bacillus oceanisediminis H2(T) (97.9%), Bacillus infantis SMC 4352-1(T) (97.4%), Bacillus firmus IAM 12464(T) (96.8%) and Bacillus muralis LMG 20238(T) (96.8%). DNA-DNA hybridization, and biochemical and physiological characterization allowed the differentiation of strain DS22(T) from its closest phylogenetic neighbours. The data supports the proposal of a novel species, Bacillus purgationiresistans sp. nov.; the type strain is DS22(T) (=DSM 23494(T)=NRRL B-59432(T)=LMG 25783(T)).

Biological decolorization of industrial dyes by Candida tropicalis and Bacillus firmus

Disperse dyes are chiefly used by textile industries for the coloration of polyester and cellulose triacetate and their blended fibres. Their extensive use and recalcitrant nature, high tinctorial strength renders the voluminous textile effluents intensively colored and causes environmental concerns. Decolorization of representative members of Dianix CC and Dianix S brands (DyStar Pvt. Ltd.) of disperse dyes were tested with Candida tropicalis and Bacillus firmus isolated respectively from contaminated soil samples and sludge of a domestic sewage drain. While both the cultures efficiently remove color from the aqueous solutions of the dyes, the yeast culture was found to decolorize most of the tested disperse dyes through biotransformation, the bacterial culture showed color removal mainly by adsorption on the cell pellets. Formation of cleavage products such as p-nitroaniline was observed in the case of Dianix Orange E-3R, indicating reductive cleavage of the azo linkage of the dye.

An Extracellullar Nuclease from Bacillus Firmus VKPACU-1: Specificity and Mode of Action

An extracellular nuclease from Bacillus firmus VKPACU-1 was multifunctional enzyme, this nuclease hydrolyzed poly U rapidly and more preferentially than the other homopolyribonucleotides. Hydrolysis of RNA this enzyme released mononucleotides in the order 5′UMP > 5′AMP > 5′GMP where as in hydrolysis of DNA the mononucleotides in the order of 5′dAMP > 5′dGMP > 5′dTMP and oligonucleotides. Uridylic linkages in RNA and adenylic linkages in DNA were preferentially cleaved by the nuclease. Nuclease produced oligonucleotides having only 3’ hydroxyl and 5’ phosphate termini. Present nuclease hydrolyzed RNA and DNA released oligonucleotides as major end products and mononucleotides, suggesting an endo mode of action.

Effect of Dye Structure on the Decolorisation Efficiency of Candida Tropicalis and Bacillus Firmus

Heterocyclic monoazo disperse dyes constitute an important class of textile colorants and are used in the coloration of hydrophobic substrates, with a large share of all the disperse dyes being used for coloration of polyester and its blends. In view of the dearth of effective methods, the need to develop protocols for decolorisation/ degradation of these dyes is fuelled. Decolorisation/degradation of heterocyclic monoazo disperse dyes were tested using Candida tropicalis and Bacillus firmus respectively isolated from dye contaminated soil samples and sludge of domestic seweage drain and the correlation of decolorisation with dye molecular structure has been drawn with the microbial decolorisation efficiency. The results reveal that there is a significant difference between the decolorizing ability of Candida tropicalis and Bacillus firmus respectively, under their respective conditions. Degradation of dyes by both these cultures was driven by a qualitatively visualized hydrophilic-hydrophobic balance of the chromophores as well as the extent to which a dye was adsorbed on cell mass.

Epizootic rabbit enteropathy inoculum (TEC4): antibiograms and antibiotic fractionation

Epizootic rabbit enteropathy (ERE) emerged and spread in Europe within the last 13years causing major economical loss. The aims of the study was to evaluate antibiograms of TEC4, an inoculum composed of an extract of intestinal content of affected rabbits, and to test the potential of different antibiotic-based TEC4 fractions to reproduce the disease. Twenty nine different antibiotic discs were incubated for determining bacteria resistance. In a complementary study, nine tubes of liquid medium were inoculated with TEC4, incubated and added individually with amoxicillin/clavulanic acid, bacitracin, ceftiofur, doxycycline, novobiocin, streptomycyin, tylosin, vancomycin and 0.9% saline solution as control. The content of each tube was washed by centrifugation and suspended in saline. The three most effective antibiotics are florfenicol, amoxycillin/clavulanic acid and tylosin. A high concentration of Clostridium sordelli and Bacillus firmus were isolated in all fractions. Species never cultured from TEC4 were identified as Fusobacterium necrogenes (in vancomycin fraction), Cellulomonas sp (in novobiocin fraction) and Bacteroides distasonis (in doxycycline fraction). The ERE was reproduced when bacitracin, doxycycline and 0.9% fractions were inoculated. Rabbits showed ERE clinical signs with the specific drop in daily weight gain.

PRODUKSI GAS HASIL BIODEGRADASI MINYAK BUMI: KAJIAN AWAL APLIKASINYA DALAM MICROBIAL ENHANCED OIL RECOVERY (MEOR)

Normal 0 false false false IN X-NONE X-NONE MicrosoftInternetExplorer4 Gas Production Generated from Crude Oil Biodegradation: Preliminary Study on its Aplication in Microbial Enhanced Oil Recovery (MEOR). The objective of this study is to observe the capacity of gas production generated from crude oil degradation by the isolated bacteria. The gas in the MEOR could increase pressure in the reservoir, decrease oil viscosity, increase oil permeability-due to the increase of the porosity and viscosity, and also increase oil volume due to the amount of dissolved gas. A research on gas analysis of oil degradation by 6 isolated bacteria has been conducted. The bacteria isolates including Bacillus badius (A), Bacillus circulans (B), Bacillus coagulans (C), Bacillus firmus (D), Pasteurella avium (E) and Streptobacillus moniliformis (F). The trial on gas production, gas analysis and oil degradation analysis, was carried out by using SMSS medium. The test of gas production was done by using microrespirometer at 40&deg;C. The result shows that B, C, D, E produce more gas than A and F. Gas of CO 2 , O 2 , CO, N 2 , CH 4 , and H 2 were &nbsp; analyzed by using GC. The results show that only three gases were detected by GC i.e. CO 2 , N 2 , and O 2 . The concentration of CO 2 and N 2 gas increased while the concentration of O 2 decreased over an 8th day of observation. CO 2 gas producted by mix culture was higher than by the pure culture. On the 8th day of incubation, the production of CO 2 gas by mix culture was 4,0452% while pure culture C and D only produced 2,4543% and 2,8729%. The mix culture increase simple &nbsp; hydrocarbon by 12.03% and the formation of a complex hydrocarbon by 3.07%. The mix culture (C-D) generated the highest concentration of CO 2 gas as well as a synergistic concortium that has ability to degrade crude oil. Keywords: degradation, mix culture, gas, crude oil, MEOR, crude oil biodegradation &nbsp;

Adjuvant effect of Bacillus firmus on the expression of cytokines and toll-like receptors in mouse nasopharynx-associated lymphoid tissue (NALT) after intranasal immunization with inactivated influenza virus type A

Due to the persisting threat of development of new highly pathogenic influenza A subtypes, a mucosal vaccination which would induce a potent and cross-protective reaction is desirable. We succeeded in mucosal immunization of mice with an inactivated influenza A virus by using delipidated Bacillus firmus (DBF) as adjuvant. The mechanism of adjuvant effect was followed in NALT by comparing the response after intranasal immunization by inactivated influenza virus type A (H1N1) alone, adjuvant alone (DBF), or by a mixture of virus + DBF. Expression of selected gene groups was tested via qPCR at 7 different time-points: cytokines (IL-2, IFN-γ, IL-4, IL-6, and IL-10), type I interferons (IFN-α4, IFN-α11, IFN-α12, and IFN-β), toll-like receptors (TLR2, TLR3, TLR7, and TLR9), iNOS and CCR7. Intranasally administered DBF and the mixture of virus + DBF induced an elevated expression of IFN-γ, IL-6 and IL-10 cytokines, type I interferons, iNOS, and pDC markers in NALT. Multimarker qPCR data was analyzed by relative quantification and by principal component analysis. DBF has been shown to be a very efficient adjuvant for the stimulation of innate immunity after IN immunization. DBF accelerated, increased, and prolonged the antiviral response.

Environmental bacteria associated with an institutional rabbit house

A bacteriological investigation of microorganisms of public health importance associated with rabbit houses was undertaken to determine the occurrence of bacteria in rabbit house in Ibadan. A total of 144 swab samples were collected from which 160 bacterial isolates were recovered. E. coli, (20%) showed the highest occurrence, followed in descending order by Staphylococcus aureus (12.5%), Proteus vulgaris (12.5%), Bacillus cereus (12.5%), Bacillus subtilis (10%), Streptococcus faecalis (10%), Bacillus firmus (7.5%), Proteus morganii (5%), Pseudomonas aureginosa (I2.5%), Streptococcus pyogenes (2.5%), Micrococcus species (2.5%) and Klebsiella species (2.5%). All the 20 (12.5%) staphylococcal isolates were coagulase-positive using tube coagulase test with human plasma. Similar strains of bacteria encountered in this investigation have been incriminated in disease outbreaks in rabbits with losses in terms of meat meant for human consumption and are therefore of public health importance. There is the need for regular microbiological surveillance to protect our growing rabbitaries and the rabbit models in biomedical research since these latent organisms may produce clinical conditions when the rabbits are exposed to stress conditions. Above all the importance of good hygiene and management in rabbitaries cannot be overemphasized to prevent avoidable outbreaks. (Afr. J. Biomed. Res. 11: 209 - 213)

Chromate Reduction by Cell-Free Extract of Bacillus firmus KUCr1

Microbial enzymatic reduction of a toxic form of chromium [Cr(VI)] has been considered as an effective method for bioremediation of this metal. This study reports on the in vitro reduction of Cr(VI) using cell-free extracts from a Cr(VI) reducing Bacillus firmus KUCr1 strain. Chromium reductase was found to be constitutive and its activity was observed both in soluble cell fractions (S12 and S150 and membrane cell fraction (P150). The reductase activity of S12 fraction was found to be optimal at 40 microM Cr(VI) with enzyme concentration equivalent to 0.493 mg protein/ml. Enzyme activity was dependent on NADH or NADPH as electron donor; optimal temperature and pH for better enzyme activity were 70 degrees C and 5.6, respectively. The Km value of the reductase was 58.33 microM chromate having a V(max) of 11.42 microM/min/mg protein. The metabolic inhibitor like sodium azide inhibited reductase activity of membrane fraction of the cell-free extract. Metal ions like Cu2+, Co2+, Ni2+ and As3+ stimulated the enzyme but others, such as Ag+, Hg2+, Zn2+, Mn2+, Cd2+ and Pb2+, inhibited Cr(VI) reductase activity.

Carotenoids found inBacillus

To identify the diversity of pigmented aerobic spore formers found in the environment and to characterize the chemical nature of this pigmentation. Sampling of heat-resistant bacterial counts from soil, sea water and the human gastrointestinal tract. Phylogenetic profiling using analysis of 16S rRNA sequences to define species. Pigment profiling using high-performance liquid chromatography-photo diode array analysis. The most commonly found pigments were yellow, orange and pink. Isolates were nearly always members of the Bacillus genus and in most cases were related with known species such as Bacillus marisflavi, Bacillus indicus, Bacillus firmus, Bacillus altitudinis and Bacillus safensis. Three types of carotenoids were found with absorption maxima at 455, 467 and 492 nm, corresponding to the visible colours yellow, orange and pink, respectively. Although the presence of other carotenoids cannot be ruled out, these three predominant carotenoids appear to account for the pigments obtained in most pigmented bacilli, and our analysis reveals the existence of a C30 biosynthetic pathway. Interestingly, we report the presence of a water-soluble pigment that may also be a carotenoid. The function of carotenoids is photoprotection, and carotenoid-containing spores exhibited significantly higher levels of resistance to UV radiation than non-carotenoid-containing Bacillus species. This study demonstrates that pigmented bacilli are ubiquitous and contain new carotenoid biosynthetic pathways that may have industrial importance.

Avaliação de métodos para manutenção e preservação de bactéria esporulada produtora da enzima CGTase

The conservation of cells without morphologic, physiologic or genetic changes is a biotechnology necessity. Bacillus firmus strain 37 is a sporulating bacteria that produces the cyclodextrin glycosyltransferase (CGTase) enzyme, which transforms starch into cyclodextrins (CDs). This study aimed to evaluate the maintenance and preservation of B. firmus strain 37 stored in a solid medium, sterile soil and in glycerol at low temperature (-70oC). In order to evaluate the best bacteria maintenance method, cell immobilization procedures were used on inorganic matrices. The immobilized cells were submitted to the initial biomass effect test and scanning electron microscopy (SEM). Periodic transfer was not an appropriate method, because the strain reduced the production of CGTase. The storage in sterile soil proved effective and the enzyme production remained constant. The conservation in low temperatures was also satisfactory, with cell counts practically the same after 360 days. The immobilization evaluated by SEM did not show any difference in the adsorption of the cells preserved by the different methods. The same happened for the initial biomass effect test, which presented higher beta-CD production when 1.5 g of cells was used.

Bacillus horneckiae sp. nov., isolated from a spacecraft-assembly clean room

Five Gram-stain-positive, motile, aerobic strains were isolated from a clean room of the Kennedy Space Center where the Phoenix spacecraft was assembled. All strains are rod-shaped, spore-forming bacteria, whose spores were resistant to UV radiation up to 1000 J m(-2). The spores were subterminally positioned and produced an external layer. A polyphasic taxonomic study including traditional biochemical tests, fatty acid analysis, cell-wall typing, lipid analyses, 16S rRNA gene sequencing and DNA-DNA hybridization studies was performed to characterize these novel strains. 16S rRNA gene sequencing and lipid analyses convincingly grouped these novel strains within the genus Bacillus as a cluster separate from already described species. The similarity of 16S rRNA gene sequences among the novel strains was >99 %, but the similarity was only about 97 % with their nearest neighbours Bacillus pocheonensis, Bacillus firmus and Bacillus bataviensis. DNA-DNA hybridization dissociation values were <24 % to the closest related type strains. The novel strains had a G+C content 35.6+/-0.5 mol% and could liquefy gelatin but did not utilize or produce acids from any of the carbon substrates tested. The major fatty acids were iso-C(15 : 0) and anteiso-C(15 : 0) and the cell-wall diamino acid was meso-diaminopimelic acid. Based on phylogenetic and phenotypic results, it is concluded that these strains represent a novel species of the genus Bacillus, for which the name Bacillus horneckiae sp. nov. is proposed. The type strain is 1P01SC(T) (=NRRL B-59162(T) =MTCC 9535(T)).

In Vitro Antimicrobial Effect of Satureja wiedemanniana Against Bacillus Species Isolated from Raw Meat Samples

In this study a total of 30 raw meat samples obtained from Ankara, Turkey were screened for the presence of Bacillus species. Among the meat samples analyzed, the predominant species isolated was Bacillus circulans; other Bacillus species were identified as Bacillus firmus, Bacillus lentus, Bacillus megaterium, Bacillus licheniformis, Bacillus mycoides, Bacillus sphaericus, and Bacillus cereus. Minced meat samples were more contaminated with Bacillus species than sliced beef sample. From these samples, 242 Bacillus species isolates were obtained, which were investigated for proteolytic and lipolytic activity, associated with meat spoilage. Interestingly, some Bacillus strains produced the highest values of proteolytic/lipolytic activities. Nineteen Bacillus strains were selected among the 242 isolates according to their proteolytic/lipolytic activity with a clear zone diameter of > or =6 mm. The essential oil of Satureja wiedemanniana (Lalem) Velen was also tested against these 19 Bacillus species that had proteolytic and lipolytic activity. The essential oil yield obtained from the aerial parts of the plant was 0.35% (vol/wt). The inhibition zones of the essential oil obtained against all the Bacillus species were in the range of 5.0-12.0 mm. The oil showed high antimicrobial activities against B. licheniformis M 6(26), M 11(16), and M 12(1) strains. B. licheniformis 12(1) showed high lipolytic activity (18.0 mm). Also, B. licheniformis M 6(26) and M 11(16) showed high proteolytic activity (16.0 and 14.0 mm). These results may suggest that an essential oil of S. wiedemanniana can be used as a natural preservative in meat against spoilage bacteria.

Screening siderophore producing bacteria as potential biological control agent for fungal rice pathogens in Thailand

Rice (Oryza sativa) is a staple food in Thailand and, in addition, feeds around one half of the world’s population. Therefore, diseases of rice are of special concern. Rice is destroyed by 2 main pathogens, Fusarium oxysporum and Pyricularia oryzae the causative agents of root rot and blast in rice respectively. These pathogens result in low grain yield in Thailand and other Southeast Asian countries. Soil samples were taken from paddy fields in Northern Thailand and bacteria were isolated using the soil dilution plate method on Nutrient agar. Isolation yielded 216 bacterial isolates which were subsequently tested for their siderophore production and effectiveness in inhibiting mycelial growth in vitro of the rice pathogenic fungi; Alternaria sp., Fusarium oxysporum, Pyricularia oryzae and Sclerotium sp., the causal agent of leaf spot, root rot, blast and stem rot in rice. It was found that 23% of the bacteria isolated produced siderophore on solid plating medium and liquid medium, In dual culture technique, the siderophore producing rhizobacteria showed a strong antagonistic effect against the Alternaria (35.4%), Fusarium oxysporum (37.5%), Pyricularia oryzae (31.2%) and Sclerotium sp. (10.4%) strains tested. Streptomyces sp. strain A 130 and Pseudomonas sp. strain MW 2.6 in particular showed a significant higher antagonistic effect against Alternaria sp. while Ochrobactrum anthropi D 5.2 exhibited a good antagonistic effect against F. oxysporum. Bacillus firmus D 4.1 inhibited P. oryzae and Kocuria rhizophila 4(2.1.1) strongly inhibited Sclerotium sp. P. aureofaciens AR 1 was the best siderophore producer overall and secreted hydroxamate type siderophore. This strain exhibits an in vitro antagonistic effect against Alternaria sp., F. oxysporum and P. oryzae. Siderophore production in this isolate was maximal after 15 days and at an optimal temperature of 30°C, yielding 99.96 ± 0.46 μg ml−1 of siderophore. The most effective isolates were identified by biochemical tests and molecular techniques as members of the Genus Bacillus, Pseudomonas and Kocuria including B. firmus D 4.1, P. aureofaciens AR1 and Kocuria rhizophila 4(2.1.1). The study demonstrated antagonistic activity towards the target pathogens discussed and are thus potential agents for biocontrol of soil borne diseases of rice in Thailand and other countries.