Serratia Fonticola Research Articles

Serratia glossinae Geiger et al. 2010 is a later synonym of Serratia fonticola Gavini et al. 1979.

Serratia glossinae DSM 22080(T) was compared with Serratia fonticola ATCC 29844(T) to clarify the taxonomic relationship of both species. 16S rRNA gene sequence comparisons demonstrated that these species share 99.6% sequence similarity. Investigation of substrate utilization profiles displayed no striking differences from the type strains of both species. DNA-DNA hybridizations between both strains showed 100% (99.9%) similarity. Therefore, the reclassification of S. glossinae as a later synonym of S. fonticola is proposed, based upon the estimated phylogenetic position derived from 16S rRNA gene sequence data, biochemical data and DNA-DNA hybridization results.

Detection of Some Enteric Pathogens in Retailed Meat

Contamination of meat at the retail level is very common. The presence of members of the family Enterobacteriaceae on the meat surface will render the meat unsafe to the consumer as they are encountered in causing food poisoning and also they reflect the hygienic standard of the butchers' shops. The current study was done to evaluate the microbiological status of retailed meat of cattle and buffaloes with special concern to Enteropathogenic Escherichia coli (EPEC) and Salmonella. A total of 100 random samples of meat of cattle and buffaloes (50 of each) were collected from different butchers' shops at Behera province. The samples were evaluated bacteriologically with a trial to isolate some enteric pathogens of public health significance. The obtained results revealed that the mean values of total Enterobacteriaceae count in examined meat samples of cattle and buffaloes were 1.4 X 104±1.4 X 103 and 2.7 X 104± 3.3 X 103 cfu/g, respectively. Also, the mean values of total Coliform count in cattle and buffaloes meat samples were 1.5 X 104±1.4 X 103, 1.8 X104± 1.8 X 103 cfu/g, respectively. In addition, isolation and identification of enteric bacteria revealed that the isolation of E. coli, Salmonella species, Enterobacter aerogenes. Enterobacter intermedium, Enterobacter gergoviae, Citrobacter amalonaticus, Citrobacter diversus, Citrobacter freundii, Serratia marcescens, Serratia ficaria, Serratia fonticola, Serratia liquefaciens. Serratia rubidaea, Edwardsiclla ictalori, Edwardsiella hoshinae, Providencia alcalifaciens, Providencia stuartii, Klebsiella pneumonia subspecies ozaenae, Proteus mirabilis. Concerning EPEC, it was found that it was detected in 32% and 40% of the examined meat samples of cattle and buffaloes, respectively. Furthermore, the serological identification of the obtained isolates of EPEC revealed the presence of the following serotypes O55: K59, O111:K58, O114:K96, O111:K69, O125:K70, O126:K71, O127:K63. On the other side, the obtained results revealed the isolation of Salmonella species at the percentage of 4 and 8 in the examined meat samples of cattle and buffaloes, respectively. Furthermore, the serological identification of the obtained isolates of Salmonella revealed the presence of S. Typhi, S. Enteritidis and S. Paratyphi. On basis of the obtained results it was observed that meat of buffaloes was more contaminated with all members of Enterobacteriaceae than meat of cattle so strict hygienic measures should be considered during slaughtering, transportation and handling of meat till reach safe for consumers.

Density- and trait-mediated effects of a parasite and a predator in a tri-trophic food web.

1. Despite growing interest in ecological consequences of parasitism in food webs, relatively little is known about effects of parasites on long-term population dynamics of non-host species or about whether such effects are density or trait mediated.2. We studied a tri-trophic food chain comprised of (i) a bacterial basal resource (Serratia fonticola), (ii) an intermediate consumer (Paramecium caudatum), (iii) a top predator (Didinium nasutum) and (iv) a parasite of the intermediate consumer (Holospora undulata). A fully factorial experimental manipulation of predator and parasite presence/absence was combined with analyses of population dynamics, modelling and analyses of host (Paramecium) morphology and behaviour.3. Predation and parasitism each reduced the abundance of the intermediate consumer (Paramecium), and parasitism indirectly reduced the abundance of the basal resource (Serratia). However, in combination, predation and parasitism had non-additive effects on the abundance of the intermediate consumer, as well as on that of the basal resource. In both cases, the negative effect of parasitism seemed to be effaced by predation.4. Infection of the intermediate consumer reduced predator abundance. Modelling and additional experimentation revealed that this was most likely due to parasite reduction of intermediate host abundance (a density-mediated effect), as opposed to changes in predator functional or numerical response.5. Parasitism altered morphological and behavioural traits, by reducing host cell length and increasing the swimming speed of cells with moderate parasite loads. Additional tests showed no significant difference in Didinium feeding rate on infected and uninfected hosts, suggesting that the combination of these modifications does not affect host vulnerability to predation. However, estimated rates of encounter with Serratia based on these modifications were higher for infected Paramecium than for uninfected Paramecium.6. A mixture of density-mediated and trait-mediated indirect effects of parasitism on non-host species creates rich and complex possibilities for effects of parasites in food webs that should be included in assessments of possible impacts of parasite eradication or introduction.

Quorum sensing activity of Serratia fonticola strain RB-25 isolated from an ex-landfill site.

Quorum sensing is a unique bacterial communication system which permits bacteria to synchronize their behaviour in accordance with the population density. The operation of this communication network involves the use of diffusible autoinducer molecules, termed N-acylhomoserine lactones (AHLs). Serratia spp. are well known for their use of quorum sensing to regulate the expression of various genes. In this study, we aimed to characterized the AHL production of a bacterium designated as strain RB-25 isolated from a former domestic waste landfill site. It was identified as Serratia fonticola using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry analysis and this was confirmed by 16S ribosomal DNA sequencing. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis of S. fonticola strain RB-25 spent culture supernatant indicated the existence of three AHLs namely: N-butyryl-L-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL) and N-(3-oxohexanoyl) homoserine-lactone (3-oxo-C6 HSL). This is the first report of the production of these AHLs in S. fonticola.

Misidentification of Providencia stuartii as Serratia fonticola by Vitek 2

"Misidentification of Providencia stuartii as Serratia fonticola by Vitek 2." British Journal of Biomedical Science, 71(3), pp. 132–133

Draft Genome Sequence of Plant-Growth-Promoting Rhizobacterium Serratia fonticola Strain AU-AP2C, Isolated from the Pea Rhizosphere

Plant health can be augmented by plant-growth-promoting rhizobacteria (PGPR) that confer biofertilizer, phytostimulation, and biocontrol activities. Herein, we provide the high-quality draft genome sequence of Serratia fonticola strain AU-AP2C, a Gram-negative motile PGPR of the pea plant, conferring phosphate solubilization, ammonia production, and antifungal activity against Fusarium sp. The 4.9-Mb genome contains genes related to plant growth promotion and synthesis of siderophores.

Draft Genome Sequence of Serratia fonticola LMG 7882 T Isolated from Freshwater

Serratia fonticola is a Gram-negative bacterium with a wide distribution in aquatic environments. On some occasions, it has also been regarded as a significant human pathogen. In this work, we report the first draft genome sequence of an S. fonticola strain (LMG 7882T), which was isolated from freshwater.

Extended spectrum ß-lactamase- and constitutively AmpC-producing Enterobacteriaceae on fresh produce and in the agricultural environment

The attribution of fresh produce to the overall community-associated exposure of humans to ESBL- or AmpC-producing bacteria is currently unknown. To address this issue, the prevalence of ESBL- and AmpC-producing Enterobacteriaceae on fresh produce produced in the Netherlands was determined. Seven vegetable types that are consumed raw were selected: blanched celery, bunched carrots, chicory, endive, iceberg lettuce, mushrooms, and radish. The vegetables were mostly obtained from supermarkets. To determine whether the agricultural environment is the source of ESBL-producing Enterobacteriaceae on fresh produce, iceberg lettuce was also obtained directly from three farms, in conjunction with soil and irrigation water. ESBL-producing Enterobacteriaceae isolated from vegetables and environment were all environmental species: Rahnella aquatilis (n=119), Serratia fonticola (n=45) and Pantoea agglomerans (n=1). ESBL genes of R. aquatilis and S. fonticola were identified as blaRAHN-1 and blaRAHN-2 and blaFONA-1, blaFONA-2, blaFONA-3/6 and blaFONA-5, respectively. For R. aquatilis and S. fonticola, different prevalence numbers were observed using different isolation methods, which could at least partially be explained by an inverse correlation between the level of cefotaxime resistance of these species and incubation temperature. R. aquatilis was isolated from 0 to 46% of soil samples and 11 to 83% of vegetable samples, and S. fonticola from 2 to 60% of soil samples and 0 to 1.3% of vegetable samples. Third generation cephalosporin-resistant faecal Enterobacteriaceae were isolated from 2.7%, 1.3% and 1.1% of supermarket vegetables, iceberg lettuce from farms, and agricultural soil respectively. Faecal Enterobacteriaceae were all identified as Citrobacter and Enterobacter species and, with the exception of one Citrobacter koseri strain, all had phenotypes indicative of constitutive AmpC production. Comparison of fresh produce and its agricultural environment indicates that the Enterobacteriaceae population on fresh produce reflects that of the soil it is grown in.Public health risks associated with exposure to ESBL- and AmpC-producing bacteria through consumption of uncooked fresh produce are diverse. They range from occasional ingestion of 3GC-resistant opportunistic pathogens which may result in difficult-to-treat infections, to frequent ingestion of relatively harmless ESBL-producing environmental bacteria that may therewith constitute a continuously replenished intestinal reservoir facilitating dissemination of ESBL genes to (opportunistic) pathogens.

Selection and evaluation of potential biocontrol rhizobacteria from a raised bog environment

Understanding the interactions of bacteria with plants and the role of microorganisms in the lifecycle of plants is becoming more and more important due to the social claim for a clean agriculture. Thus the significance of studying plant associated bacteria is increasing. The main aim of our study was to isolate and characterize bacteria associated with bryophytes from a natural raised bog ecosystem. Characterization of the isolates by their beneficial properties was realized with microbiological and molecular tools. Bacterial strains were identified taxonomically, isolates belonging to the genera Pseudomonas, Bacillus, Serratia, Stenotrophomonas, Delftia, Cedecea, Lysinibacillus and Viridibacillus have been found. Pseudomonas, Serratia and Bacillus were the dominant bacterial genera associated with bryophytes. In vitro study of antagonism showed that a high number of the isolates inhibited the growth of fungal and bacterial plant pathogens – Fusarium oxysporum, Alternaria alternata, Erwinia carotovora – or produced secondary metabolic substances with biocontrol properties. Bacterial strains identified as Serratia fonticola BB17 and Pseudomonas fluorescens BE8 proved to be the most efficient against plant pathogens, with biocontrol effectiveness up to 48.28% and 55.17% respectively, suggesting the potential use of these strains in biotechnological applications.

Adhesion to brown trout skin mucus, antagonism against cyst adhesion and pathogenicity to rainbow trout of some inhibitory bacteria against Saprolegnia parasitica

Biological control of saprolegniosis with bacteria might be an alternative to the use of chemical compounds. Among criteria for the selection of such bacteria are their absence of pathogenicity to fish and their ability to prevent adhesion of the pathogen to the skin mucus. The pathogenicity to rainbow trout of 21 bacterial isolates with in vitro inhibitory activity against Saprolegnia parasitica was studied. Fifteen of the isolates, identified as Aeromonas sobria, Pantoea agglomerans, Pseudomonas fluorescens, Serratia fonticola, Xanthomonas retroflexus and Yersinia kristensenii, were non-pathogenic when injected into rainbow trout. Their capacity to adhere to the skin mucus of male and female brown trout and to reduce the adhesion of S. parasitica cysts under exclusion, competition and displacement conditions was tested. The 15 bacterial isolates showed a low adhesion rate, ranging between 1.7% (for an A. sobria isolate) and 15.3% (a P. fluorescens isolate). This adhesion was greater in the case of mucus from male brown trout than from females. Similarities in the adhesion to male mucus and other substrates and correlation to that observed to polystyrene suggest that adhesion to skin mucus does not depend on the substrate. A high percentage (88.9%) of the S. parasitica cysts adhered to the skin mucus of male brown trout. Almost all of the bacteria reduced this adhesion ratio significantly under exclusion and competition conditions. However, only half of the isolates displaced cysts from skin mucus, and more bacterial cells were necessary for this effect. A novel method to study the adhesion of S. parasitica cysts to skin mucus of trout and their interactions with inhibitory bacteria is described.

Characterization of an extended-spectrum class A β-lactamase from a novel enterobacterial species taxonomically related to Rahnella spp./Ewingella spp.

To characterize the naturally occurring β-lactamase gene identified from a clinical isolate belonging to a novel enterobacterial species that is closely related to Rahnella spp. and Ewingella spp. Shotgun cloning and expression in Escherichia coli were performed in order to characterize this resistance determinant. Enzymatic activities were measured by UV spectrophotometry after an ion-exchange chromatography purification procedure. A chromosomal gene coding for the extended-spectrum β-lactamase (ESBL) SMO-1 was identified from a novel enterobacterial species that is taxonomically related to Rahnella aquatilis and Ewingella americana. The β-lactamase efficiently hydrolysed penicillins and cefotaxime, and shared 75% amino acid identity with the plasmid-mediated β-lactamase SFO-1 from Serratia fonticola, 74% amino acid identity with the plasmid-mediated ESBL CTX-M-2 originating from Kluyvera spp. and 72% amino acid identity with the chromosomally encoded and intrinsic RAHN-1 from R. aquatilis. We have identified a novel enterobacterial species recovered from a clinical specimen, constituting another potential source of acquired ESBL. The ESBL shared significant similarities with the CTX-M-type enzymes.

Characterization of Serratia fonticola, an opportunistic pathogen isolated from drinking water

We characterized the ST2 strain of Serratia fonticola isolated from drinking water of a capping spring on Mt. Vlasina. The ST2 strain isolated from bottled water showed the characteristics of Enterobacteriaceae family but not of the Serratia genus. S. fonticola belongs to a group of opportunistic pathogens and can cause illness in people with weak or damaged immune systems. A biochemical characterization of the strain was made by using the identification system API (bioMèrieux®). Molecular characterization was done by PCR amplification of 16S rDNA gene using the thermal cycling sequencing method and by sequencing. By comparing the obtained 1016 nucleotide sequence with the NCBI collection of all deposited sequences for 16S rDNK, and by using the BLAST search service, the highest identity (98% uniformity) was obtained with the S. fonticola strain, designated as LMG 7882 (gi|15054669|gb|AF286869.1). The identity of 16S rDNA between the referent strain and ST2 is not absolute, indicating an autochthonous origin of strain ST2.

Predominant enterobacteria on modified-atmosphere packaged meat and poultry

Enterobacteria on modified-atmosphere (MA) packaged meat (n = 54) and poultry (n = 32) products were enumerated, and 899 isolates were picked and ribotyped. For identification, 16S rRNA genes of representative strains were sequenced and analyzed. Altogether 54 (60%) of the samples contained enterobacteria >104 CFU/g. In 34% of the poultry samples, enterobacteria counts were >106 CFU/g suggesting that enterobacteria may contribute to spoilage of MA packaged poultry. The enterobacteria identified were predominantly Hafnia spp. (40%) and Serratia spp. (42%) with Hafnia alvei, Hafnia paralvei, Serratia fonticola, Serratia grimesii, Serratia liquefaciens, Serratia proteamaculans, and Serratia quinivorans being the species identified. In addition, 6% of the isolates were identified as Rahnella spp., 3% as Yersinia spp., and 1% as Buttiauxella spp. Percentage distributions of the predominant genera in different products showed that 89% of the Serratia spp. were from products packaged under a high-O2 MA containing CO2 (25–35%), whereas most (76%) isolates of Hafnia originated from anaerobically packaged red meat and poultry. These findings suggest that the gas mixture used for MA packaging influence the selection of enterobacteria growing on meat and poultry.

The Basis for Carbapenem Hydrolysis by Class A β-Lactamases: A Combined Investigation using Crystallography and Simulations

Carbapenems are the most potent β-lactam antibiotics and key drugs for treating infections by Gram-negative bacteria. In such organisms, β-lactam resistance arises principally from β-lactamase production. Although carbapenems escape the activity of most β-lactamases, due in the class A enzymes to slow deacylation of the covalent acylenzyme intermediate, carbapenem-hydrolyzing class A β-lactamases are now disseminating in clinically relevant bacteria. The reasons why carbapenems are substrates for these enzymes, but inhibit other class A β-lactamases, remain to be fully established. Here, we present crystal structures of the class A carbapenemase SFC-1 from Serratia fonticola and of complexes of its Ser70 Ala (Michaelis) and Glu166 Ala (acylenzyme) mutants with the carbapenem meropenem. These are the first crystal structures of carbapenem complexes of a class A carbapenemase. Our data reveal that, in the SFC-1 acylenzyme complex, the meropenem 6α-1R-hydroxyethyl group interacts with Asn132, but not with the deacylating water molecule. Molecular dynamics simulations indicate that this mode of binding occurs in both the Michaelis and acylenzyme complexes of wild-type SFC-1. In carbapenem-inhibited class A β-lactamases, it is proposed that the deacylating water molecule is deactivated by interaction with the carbapenem 6α-1R-hydroxyethyl substituent. Structural comparisons with such enzymes suggest that in SFC-1 subtle repositioning of key residues (Ser70, Ser130, Asn132 and Asn170) enlarges the active site, permitting rotation of the carbapenem 6α-1R-hydroxyethyl group and abolishing this contact. Our data show that SFC-1, and by implication other such carbapenem-hydrolyzing enzymes, uses Asn132 to orient bound carbapenems for efficient deacylation and prevent their interaction with the deacylating water molecule.

In vitro and In vivo antimicrobial activity of propolis on the microbiota from gastrointestinal tract of chickens

The aim of this study was to examine the effect of propolis extracts on the microbial colonization of chicken gastrointestinal tract in vivo. The propolis was administered to both feed mixtures in various amounts except of the control group. The addition of 150 mg propolis to 1 kg of feed was included in the first experimental group, the addition of 450 mg.kg−1 in the second experimental group, the addition of 600 mg.kg−1 the third experimental group and 800 mg kg−1 in the fourth one. The highest count of faecal enterococci was found in the third group (8.6 cfu.g−1) where 600 mg of propolis to 1 kg was added to the feed mixture. The highest count of lactobacilli was detected in the fourth experimental group (8.83 cfu.g−1) where was 800 mg of propolis added to 1 kg of feed mixture and number of Enterobacteriaceae genera count was found in control group (8.73 cfu.g−1). With RTQ PCR detected species from the genus Enterococcus were: E. avium, E. casseliflavus, E cecorum, E. faecalis, E. faecium, E. gallinarum, E. hirae and E. malodoratus and from genus Lactobacillus were: Lactobacillus crispatus, L. acidophilus and L. salivarius. With MALDI TOF MS Biotyper from Enterobacteriaceae genera were identified Citrobacter braakii, Raoultella ornithinolytica, Serratia fonticola, Escherichia coli and Klebsiella oxytoca. Antimicrobial activities In vitro of six species of bacteria isolated from gastrointestinal tract of chickens were also tested. The best antimicrobial effect of Citrobacter braakii on ethanolic propolis extract in all concentrations were found.

On the active site of mononuclear B1 metallo β-lactamases: a computational study

Metallo-β-lactamases (MβLs) are Zn(II)-based bacterial enzymes that hydrolyze β-lactam antibiotics, hampering their beneficial effects. In the most relevant subclass (B1), X-ray crystallography studies on the enzyme from Bacillus Cereus point to either two zinc ions in two metal sites (the so-called '3H' and 'DCH' sites) or a single Zn(II) ion in the 3H site, where the ion is coordinated by Asp120, Cys221 and His263 residues. However, spectroscopic studies on the B1 enzyme from B. Cereus in the mono-zinc form suggested the presence of the Zn(II) ion also in the DCH site, where it is bound to an aspartate, a cysteine, a histidine and a water molecule. A structural model of this enzyme in its DCH mononuclear form, so far lacking, is therefore required for inhibitor design and mechanistic studies. By using force field based and mixed quantum-classical (QM/MM) molecular dynamics (MD) simulations of the protein in aqueous solution we constructed such structural model. The geometry and the H-bond network at the catalytic site of this model, in the free form and in complex with two common β-lactam drugs, is compared with experimental and theoretical findings of CphA and the recently solved crystal structure of new B2MβL from Serratia fonticola (Sfh-I). These are MβLs from the B2 subclass, which features an experimentally well established mono-zinc form, in which the Zn(II) is located in the DCH site. From our simulations the εεδ and δεδ protomers emerge as possible DCH mono-zinc reactive species, giving a novel contribution to the discussion on the MβL reactivity and to the drug design process.

Larval parasitoids and larval diseases of Malacosoma neustria L. (Lepidoptera: Lasiocampidae) detected in Erzurum Province, Turkey

The larval parasitoids and larval diseases of Malacosoma neustria (L.) (Lepidoptera: Lasiocampidae) in various host plants were investigated in Erzurum Province, Turkey, during 2004 and 2005. The larval parasitoids were reared in a laboratory, and a total of 29 parasitoid species were established in association with the larvae of M. neustria in the families Tachinidae (Diptera), Braconidae, Ichneumonidae, and Chalcidoidea (Hymenoptera). Of the 6 tachinid parasitoids, Pales pavida (Meigen) was the most prevalent species and accounted for 25% of the tachinid records. Among the tachinids, there were 2 new records for the Turkish fauna: Exorista amoena Mesnil and Palesisa nudioculata Villeneuve. Exorista amoena was reared from M. neustria for the first time. The braconid species Meteorus lionotus Thomson and Cotesia vanessa (Reinhard) were also reared from M. neustria for the first time. Among the 10 chalcidoid species reared, Monodontomerus aereus Walker and Brachymeria secundaria (Rusc.) were the most prevalent species. Five chalcidoid species, Asaphes suspensus (Nees), A. vulgaris Walker (Pteromalidae), Brachymeria secundaria (Ruschka) (Chalcididae), Eupelmus urozonus Dalman (Eupelmidae), and Eurytoma verticillata (F.) (Eurytomidae), were reared from M. neustria for the first time. Of the 10 species of ichneumonids reared, Exeristes roborator F. was the most abundant and accounted for 35% of the total ichneumonid records. The total parasitism rate of all parasitoids was 33.7%. As disease agents of M. neustria, the nuclear polyhedrosis virus and 4 pathogenic bacteria, Brevibacillus agri, Alcaligenes xylosoxydans xylosoxydans (Achromobacter xylosoxidans), Bacillus lentimorbus, and Serratia fonticola, were diagnosed. All of the bacteria from M. neustria were recorded for the first time. The percentage of diseased larvae was low, about 3%.

Crystal Structure of Serratia fonticola Sfh-I: Activation of the Nucleophile in Mono-Zinc Metallo-β-Lactamases

Metallo-β-lactamases (MBLs) or class B β-lactamases are zinc-dependent enzymes capable of inactivating almost all classes of β-lactam antibiotics. To date, no MBL inhibitors are available for clinical use. Of the three MBL subclasses, B2 enzymes, unlike those from subclasses B1 and B3, are fully active with one zinc ion bound and possess a narrow spectrum of activity, hydrolyzing carbapenem substrates almost exclusively. These remain the least studied MBLs. Sfh-I, originally identified from the aquatic bacterium Serratia fonticola UTAD54, is a divergent member of this group. Previous B2 MBL structures, available only for the CphA enzyme from Aeromonas hydrophila, all contain small molecules bound in their active sites. In consequence, the mechanism by which these enzymes activate the water nucleophile required for β-lactam hydrolysis remains to be unambiguously established. Here we report crystal structures of Sfh-I as a complex with glycerol and in the unliganded form, revealing for the first time the disposition of water molecules in the B2 MBL active site. Our data indicate that the hydrolytic water molecule is activated by His118 rather than by Asp120 and/or zinc. Consistent with this proposal, we show that the environment of His118 in B2 MBLs is distinct from that of the B1 and B3 enzymes, where this residue acts as a zinc ligand, and offer a structure-based mechanism for β-lactam hydrolysis by these enzymes.

Comparative effectiveness of Pseudomonas and Serratia sp. containing ACC-deaminase for coinoculation with Rhizobium leguminosarum to improve growth, nodulation, and yield of lentil

Three plant growth-promoting rhizobacteria strains containing ACC-deaminase (Pseudomonas jessenii, Pseudomonas fragi, and Serratia fonticola) and Rhizobium leguminosarum were selected and characterized by conducting some experiments under axenic condition. The selected isolates had the potential to improve the growth of lentil seedlings under axenic conditions. Pot and field experiments were conducted to evaluate the potential of these selected strains for improving growth and yield of lentil under natural conditions. A classical triple response (reduction of stem elongation, swelling of hypocotyle, and change in the direction of growth) bioassay was also conducted to evaluate the effect of high ethylene concentration on the growth of etiolated lentil seedlings, and the performance of coinoculation was evaluated to reduce the classical triple response in comparison with cobalt (Co2+), a chemical inhibitor of ethylene. Results showed that coinoculation of Pseudomonas and Serratia sp. with R. leguminosarum significantly increased the growth and yield of lentil. However, synergistic/coinoculation effect of P. jessenii with R. leguminosarum was more pronounced compared to that with P. fragi and S. fonticola. It increased the number of pods per plant, number of nodules per plant, dry nodule weight, grain yield, and straw yield up to 76%, 196%, 109%, 150%, and 164% under pot and up to 98%, 98%, 100%, 82%, and 78%, respectively, under field conditions as compared to uninoculated control. Similarly, combined inoculation significantly increased N concentration of grains under both pot and field conditions. The results from classical triple response assay showed that the effects of classical triple response decreased due to coinoculation in etiolated lentil seedlings and due to a decrease in the ethylene concentration. It is suggested that the strategy adopted by Pseudomonas sp. containing ACC-deaminase with Rhizobium to promote nodulation and yield by adjusting ethylene levels could be exploited as an effective tool for improving growth, nodulation, and yield of lentil.

Isolation of chromium resistant bacteria from a former bauxite mine area and their capacity for Cr (VI) reduction.

The Cr (VI) reducing capacity of bacteria has been investigated in many different soils and waters but little or no information is available from soils originating from bauxite mine areas. From soil, mud and rhizospheres of the floating aquatic plant Potamogeton natan s L. and the terrestrial plant Carduus acanthoides L., the Cr content was determined and the microbial populations were sampled. The highest total chromium concentration (204.6 mgkg -1 ) was found in the rhizosphere of C. acanthoides . To determine the numbers and percentages of chromate-resistant bacteria, the autochthonous microbial populations were subjected to different Cr (VI) concentrations (40, 100, 300 and 1000 mM as K 2 Cr 2 O 7 ). At 1000 mM Cr (VI) in the medium, about 25% of bacteria from soil and 45% of bacteria from the rhizospheres were resistant. Of 34 bacterial isolates, within 24 h, only Bacillus stearothermophilus 12 ms, Pseudomonas sp. 12 bk3 and Serratia fonticola 7 be were able to reduce 50 μM Cr (VI). Using prolonged 72 h incubation, they were able to reduce 500 μM Cr (VI) concentrations added to the medium. These chromate-resistant bacteria isolated from rhizosphere of plants growing in bauxite mine soil have great potential for bioremediation of Cr (VI)-polluted wastes. Key words : Chromate-resistant bacteria, chromate reduction, bauxite mine, rhizosphere, plants