Sp Strain Research Articles

Characterization of novel conjugative multiresistance plasmids carryingcfrfrom linezolid-resistantStaphylococcus epidermidisclinical isolates from Italy

The objective of this study was to investigate the genetic environment of the cfr gene from two linezolid-resistant clinical isolates of Staphylococcus epidermidis from Italy. The two strains (SP1 and SP2) were phenotypically and genotypically characterized. Transferability of cfr was assessed by electrotransformation and conjugation. The genetic contexts of cfr were investigated by PCR mapping, sequencing and comparative sequence analyses. SP1 and SP2 belonged to ST23 and ST83, respectively. In both strains, the cfr gene was located on a plasmid, which could be transferred to Staphylococcus aureus by transformation and conjugation. In isolate SP1, linezolid resistance mediated by mutations in 23S rRNA and the L3 ribosomal protein was also detected. pSP01, the cfr-carrying plasmid from strain SP1, had a larger number of additional resistance genes and was sequenced (76 991 bp). It disclosed a distinctive mosaic structure, with four cargo regions interpolated into a backbone 95% identical to that of S. aureus plasmid pPR9. Besides cfr, resistance genes distributed in the cargo regions included blaZ, lsa(B), msr(A) and aad, and a gene cluster for resistance to heavy metals. A closely related cfr plasmid (pSP01.1, ∼ 49 kb), differing from pSP01 by the lack of a large cargo region with some resistance genes, was detected in strain SP2. The conjugative multiresistance plasmid pSP01 is the first cfr-carrying plasmid to be sequenced in Italy. This is the first time cfr has been found: (i) in association with blaZ, msr(A) and heavy metal resistance genes; and (ii) in an S. epidermidis strain (SP2) belonging to ST83.

Temperature and pressure adaptation of a sulfate reducer from the deep subsurface.

Microbial life in deep marine subsurface faces increasing temperatures and hydrostatic pressure with depth. In this study, we have examined growth characteristics and temperature-related adaptation of the Desulfovibrio indonesiensis strain P23 to the in situ pressure of 30 MPa. The strain originates from the deep subsurface of the eastern flank of the Juan de Fuca Ridge (IODP Site U1301). The organism was isolated at 20°C and atmospheric pressure from ~61°C-warm sediments approximately 5 m above the sediment–basement interface. In comparison to standard laboratory conditions (20°C and 0.1 MPa), faster growth was recorded when incubated at in situ pressure and high temperature (45°C), while cell filamentation was induced by further compression. The maximum growth temperature shifted from 48°C at atmospheric pressure to 50°C under high-pressure conditions. Complementary cellular lipid analyses revealed a two-step response of membrane viscosity to increasing temperature with an exchange of unsaturated by saturated fatty acids and subsequent change from branched to unbranched alkyl moieties. While temperature had a stronger effect on the degree of fatty acid saturation and restructuring of main phospholipids, pressure mainly affected branching and length of side chains. The simultaneous decrease of temperature and pressure to ambient laboratory conditions allowed the cultivation of our moderately thermophilic strain. This may in turn be one key to a successful isolation of microorganisms from the deep subsurface adapted to high temperature and pressure.

Kiloniella litopenaei sp. nov., isolated from the gut microflora of Pacific white shrimp, Litopenaeus vannamei.

A cream-coloured rod-shaped bacterium, designated strain P1-1(T), was isolated from the gut microflora of Pacific white shrimp (Litopenaeus vannamei) from the Taiwan Strait, China. P1-1(T) was was found to be Gram-negative, oxidase and catalase positive and motile by means of a single flagellum. Growth is observed at salinities of 0.5-7% (w/v; optimum 3%), at pH 6.0-10.0 (optimum pH 7.0-9.0) and at 15-37°C (optimum 28-32°C). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain P1-1(T) belongs to the genus Kiloniella, and is closely related to Kiloniella spongiae MEBiC09566(T) (99.0% similarity), followed by Kiloniella laminariae LD81(T) (96.6% similarity). The genomic ANIm value between strain P1-1(T) and K. spongiae MEBiC09566(T) was found to be 81.7%. The DNA-DNA hybridization estimate between strains P1-1(T) and MEBiC09566(T) was 24.6%. The principal fatty acids detected were identified as summed feature 8 (C18:1 ω6c/C18:1 ω7c, 74.2%) and summed feature 3 (C16:1 ω6c/C16:1 ω7c, 9.7%). The G+C content of the chromosomal DNA, determined from the draft genome sequence, was found to be 46.1mol%. The major respiratory quinone was determined to be Q-9, while the major polar lipids are phosphatidylethanolamine, phosphatidylglycerol, three unidentified phospholipids, one unidentified aminolipid and nine unidentified lipids. The combined genotypic and phenotypic data indicate that strain P1-1(T) represents a novel species within the genus Kiloniella, for which the name Kiloniella litopenaei sp. nov. is proposed, with the type strain P1-1(T) (=MCCC 1A09869(T)=LMG 27755(T)).

Achromobacter denitrificans strain SP1 produces an intracellular esterase upon utilizing di(2ethylhexyl)phthalate

Production of an esterase by Achromobacter denitrificans strain SP1 – a di(2-ethylhexyl)phthalate (DEHP) degrading novel bacterium – in a modified basal salt medium supplemented with DEHP as an inducer-cum-additional carbon source was studied. The Plackett–Burman and Box–Behnken designs were applied to statistically optimize the production parameters, which resulted in an increase of esterase production by 24%. For the production of the maximum (30.5 U) intracellular esterase, 10 mM DEHP and 72 h incubation at pH 8.0 were found as optimum conditions; while the predicted value was 28.8 U with a correlation coefficient of 0.932; which signifies the fitness of the model. The optimum activity of the 2.5 folds purified esterase was 89.5 U with 20 mM para-nitrophenyl acetate as substrate (50 °C, pH 8.0 and for 30 min), and various metal ions were found to retarde the esterase activity. The approximate MW of partially purified esterase was 53 kDa, and the activity of esterase was also confirmed by native-PAGE. The Km and Vmax values of esterase were 1.308 mM and 62.52 μmol min−1 mg−1, respectively. Briefly, this was the first report on an enzyme from the DEHP degrading A. denitrificans SP1, which in comparison with esterase from other phthalate degrading bacteria and fungi showed better Km and Vmax.

Purification and characterization of detergent stable alkaline protease from Bacillus amyloliquefaciens SP1 isolated from apple rhizosphere.

A thermostable extracellular alkaline protease producing Bacillus amyloliquefaciens SP1 was isolated from apple rhizosphere having multifarious plant growth promoting activities. Strain SP1 was purified to 6.48-fold using four-step purification protocol and characterized in detail for its robustness and ecofriendly application in leather and detergent industries. Structural analysis revealed that the protease was monomeric and had a molecular weight of 43 kDa. It exhibited optimum activity at 60°C in alkaline environment (pH 8.0) and stable in the presence of surfactants and oxidizing agents. Enzyme was thermostable at 50°C and retained more than 70% activity after 30 min incubation. It has shown stain removal property and dehairing of goat skin without chemical assistance and hydrolyzing fibrous proteins. This protease showed Km of 0.125 mg ml(-1) and V(max) of 12820 μg ml(-1) indicating its excellent affinity and catalytic role. Thermal inactivation of the pure enzyme followed first-order kinetics. The half life of the pure enzyme at 50, 60, and 65°C was 77, 19.80, and 13.33 min, respectively. The activation energy was 37.19 KJ mol(-1). The results suggest that the B. amyloliquefaciens SP1 has a potential application in different industries.

Control of Shigatoxin-producing Escherichia coli in cheese by dairy bacterial strains

Bio-preservation could be a valuable way to control Shigatoxin-producing Escherichia coli (STEC) in cheese. To this end, 41 strains were screened for their inhibitory potential on model cheese curd and on pasteurized and raw milk uncooked pressed cheeses. Strains of Lactococcus lactis, Lactococcus garvieae, Leuconostoc pseudomesenteroides, Leuconostoc citreum, Lactobacillus sp, Carnobacterium mobile, Enterococcus faecalis, Enterococcus faecium, Macrococcus caseolyticus and Hafnia alvei reduced STEC O26:H11 counts by 1.4–2.5 log cfu g−1 and to a lesser extent STEC O157:H7 counts in pasteurized milk cheeses. Some strains can act in synergy to inhibit STEC in raw milk uncooked pressed cheeses. Inhibitory associations had no adverse effect on the sensory characteristics of these cheeses. The association of H. alvei, Lactobacillus plantarum and Lc. lactis was the most inhibitory: after inoculation of this consortium into milk, STEC O26:H11 and O157:H7, inoculated at 2 log cfu ml−1, were reduced by up to 3 log cfu g−1 in ripened cheese. Inhibition in cheese cannot be predicted from H2O2 production in BHI medium, decreased pH or milk reduction. It is not clear what role the rapid decrease in pH during the first 6 h may play in the inhibition. Further studies will be needed to determine the nature of the inhibition.

Screening of immunomodulatory and adhesive Lactobacillus with antagonistic activities against Salmonella from fermented vegetables.

The purpose of this study was to select strains of lactic acid bacteria (LAB) by their in vitro adhesive and immunomodulatory properties for potential use as probiotics. In this study, 16 randomly selected LAB strains from fermented vegetables (sauerkraut, bean and cabbage) were first screened for their tolerance to acid, bile salts, pepsin and pancreatin, bacterial inhibitory activities and abilities to adherence to Caco-2 cells. Then, 4 strains with the highest adhesion abilities were selected for further studies of their immunomodulatory properties and inhibitory effects against Salmonella adhesion and invasion to Caco-2 cells in vitro. The results showed that these 16 LAB strains effectively survived in simulated gastrointestinal condition and inhibited growth of six tested pathogens. Lactobacillus rhamnosus P1, Lactobacillus plantarum P2, Lactobacillus rhamnosus P3 and Lactobacillus casei P4 had the highest abilities to adhere to Caco-2 cells. Furthermore, L. plantarum P2 strain showed higher abilities to induce expression of tumor necrosis factor-α and interleukin-12 by splenic monocytes and strongly inhibited the adhesion and invasion of S. enteritidis ATCC13076 to Caco-2 cells. These results suggest that Lactobacillus strains P2 could be used as a probiotic candidate in food against Salmonella infection.

Draft Genome Sequence of Rhodococcus ruber Strain P25, an Active Polychlorinated Biphenyl Degrader.

We report the 5,728,255-bp draft genome sequence of Rhodococcus ruber P25, isolated from a soil polluted with halogenated aromatic compounds in the city of Perm, Russia. The strain degrades polychlorinated biphenyls and a broad range of aromatic compounds. It possesses genes that mediate the degradation of biphenyls/polychlorinated biphenyls, naphthalene, and monoaromatic compounds.

Effect of azospirillum lectins on the activity of proteolytic enzymes and their inhibitors in wheat seedling roots

The lectins of associative nitrogen-fixing strains Azospirillum brasilense Sp7 and Sp245 were shown to exerte a multidirectional effect on the activity of acidic (pH 3.5), neutral (6.8), and alkaline (pH 7.8) proteinases. The lectin of the epiphytic A. brasilense Sp7 decreased proteolytic activity at all pH values, whereas the lectin of the endophytic A. brasilense Sp245 activated neutral and alkaline proteinases, while not affecting the alkaline ones. Experiments with protease inhibitors made it possible to conclude that the lectins of the studied A. brasilense strains alter the ratio between the activities of different protease types in germinating seeds. The activity of trypsin inhibitors in wheat seedling roots was found to increase in the presence of the lectins. Our results indicate a broader spectrum of effects of azospirilla lectins on the host plant organism.

Diversity of exophillic acid derivatives in strains of an endophytic Exophiala sp.

Members of the fungal genus Exophiala are common saprobes in soil and water environments, opportunistic pathogens of animals, or endophytes in plant roots. Their ecological versatility could imply a capacity to produce diverse secondary metabolites, but only a few studies have aimed at characterizing their chemical profiles. Here, we assessed the secondary metabolites produced by five Exophiala sp. strains of a particular phylotype, isolated from roots of Microthlaspi perfoliatum growing in different European localities. Exophillic acid and two previously undescribed compounds were isolated from these strains, and their structures were elucidated by spectroscopic methods using MS, 1D and 2D NMR. Bioassays revealed a weak activity of these compounds against disease-causing protozoa and mammalian cells. In addition, 18 related structures were identified by UPLC/MS based on comparisons with the isolated structures. Three Exophiala strains produced derivatives containing a β-d-glucopyranoside moiety, and their colony morphology was distinct from the other two strains, which produced derivatives lacking β-d-glucopyranoside. Whether the chemical/morphological strain types represent variants of the same genotype or independent genetic populations within Exophiala remains to be evaluated.

Preservation of Helicobacter pylori CagA Translocation and Host Cell Proinflammatory Responses in the Face of CagL Hypervariability at Amino Acid Residues 58/59.

Carriage of the CagA oncoprotein by the human gastric cancer-associated pathogen Helicobacter pylori is significantly associated with this typically benign chronic infection advancing to a potentially fatal outcome. However it remains to be elucidated why only a small subset of individuals infected with H. pylori CagA-positive strains develops gastric cancer. H. pylori translocates CagA into host cells using a type IV secretion apparatus that interacts with host integrin receptors via a three-amino-acid-residue RGD motif on the H. pylori protein CagL. The RGD motif of CagL also plays a major role in the induction of proinflammatory responses. Upstream of this motif is a conserved glycine flanked by four hypervariable amino acid residues (residues 58, 59, 61 and 62). Certain amino acid polymorphisms at 58 and 59 are significantly prevalent in strains from gastric cancer patients in particular geographic regions; Y58E59 is seen in Taiwan and D58K59 in India. In light of the seemingly contradictory findings of recent CagL mutagenesis studies, we have examined the contribution of sequence promiscuity specifically at CagL residues 58 and 59 to CagA translocation and H. pylori-mediated proinflammatory responses of gastric epithelial cells. Using isogenic mutants of H. pylori strains P12 and 26695 with amino acid substitutions at CagL residues 58 and 59, we determined that carriage of the polymorphisms Y58E59, D58K59, D58E59, N58E59 or N58K59 did not significantly alter the capacity of H. pylori to translocate CagA into, or induce IL-8 secretion in, host cells. Our findings, together with other recently published data, suggest that the variation at CagL residues 58 and 59 does not influence type IV secretion system function in isolation, but rather may work in concert with particular polymorphisms elsewhere in CagL to modulate disease progression.

Application of internal standard method in recombinant luminescent bacteria test

Mercury and its organic compounds have been of severe concern worldwide due to their damage to the ecosystem and human health. The development of effective and affordable technology to monitor and signal the presence of bioavailable mercury is an urgent need. The Mer gene is a mercury-responsive resistant gene, and a mercury-sensing recombinant luminescent bacterium using the Mer gene was constructed in this study. The mer operon from marine Pseudomonas putida strain SP1 was amplified and fused with prompterless luxCDABE in the pUCD615 plasmid within Escherichia coli cells, resulting in pTHE30–E. coli. The recombinant strain showed high sensitivity and specificity. The detection limit of Hg2+ was 5nmol/L, and distinct luminescence could be detected in 30min. Cd2+, Cu2+, Zn2+, Ca2+, Pb2+, Mg2+, Mn2+, and Al3+ did not interfere with the detection over a range of 10−5–1mM. Application of recombinant luminescent bacteria testing in environmental samples has been a controversial issue: especially for metal-sensing recombinant strains, false negatives caused by high cytotoxicity are one of the most important issues when applying recombinant luminescent bacteria in biomonitoring of heavy metals. In this study, by establishing an internal standard approach, the false negative problem was overcome; furthermore, the method can also help to estimate the suspected mercury concentration, which ensures high detection sensitivity of bioavailable Hg2+.

Monitoring survival of phenanthrene-utilizing Sphingobium sp. P2 in soil microcosms using green fluorescent protein as a marker

Phenanthrene is a polycyclic aromatic hydrocarbon which belongs to a class of toxic environmental pollutants that has been accumulating due to a variety of anthropogenic activities. We attempted to use Sphingobium sp. P2, which is capable of utilizing phenanthrene as its sole source of carbon and energy, in bioaugmentation treatments. For successful bioremediation, monitoring the survival and metabolic activity of bioaugmented bacteria are required. This study aimed to use green fluorescent protein as a marker to estimate the survival of Sphingobiumsp. P2 in bioaugmented soil microcosms. The gfp was integrated via Tn5 transposition into the chromosome of strain P2. The gfp-inserted strains were identified by green fluorescence emission under UV light. The gfp was stably maintained in strain P2, and the strain still retained the ability to use phenanthrene as a sole carbon and energy source. Soil microcosm experiments revealed that survival of the strain P2-gfp and its phenanthrene-degrading capacity may depend on indigenous microorganisms and nutrients in the soils. The strain P2-gfp can be used to evaluate the success of bioaugmentation.

Azospirillum brasilense Enhances Recycling of Fish Effluent to Support Growth of Tomato Seedlings

Increasing environmental concerns and growing demand for safer and sustainable food production presents significant challenges for agricultural production. One potential technique, which could help improve crop productivity without adverse impact on the environment, is the use of beneficial microbes in crop production systems. This study evaluated the effects of three Azospirillum brasilense strains on tomato seedlings fertilized with effluent from freshwater fish aquaculture. Seeds were inoculated with A. brasilense strains Sp7, Sp7-S and Sp245 before sowing and after transplanting. Seedlings were raised under controlled greenhouse conditions with natural light. Inoculated seedlings produced longer roots (67%), bigger leaves (22%), higher seedling biomass (>33%), and greater protein (15%) and endogenous plant IAA (94%) contents. Inoculation with Sp7 and Sp245 increased the number of leaves and stem diameter by 8 and 10%, respectively. Seedling height was also increased by inoculation, but only with Sp7. In addition, seedlings inoculated with strains Sp7-S and Sp245 had higher total phosphorus content, while inoculation with Sp245 increased the activity of the enzyme peroxidase, which suggests that plant defense responses had been triggered. The result demonstrates the potential of the applied A. brasilense strains to enhance the usefulness of fish effluent as fertilizer for tomato seedling production.

Carotenoids are essential for the assembly of cyanobacterial photosynthetic complexes

In photosynthetic organisms, carotenoids (carotenes and xanthophylls) are important for light harvesting, photoprotection and structural stability of a variety of pigment–protein complexes. Here, we investigated the consequences of altered carotenoid composition for the functional organization of photosynthetic complexes in wild-type and various mutant strains of the cyanobacterium Synechocystis sp. PCC 6803.Although it is generally accepted that xanthophylls do not play a role in cyanobacterial photosynthesis in low-light conditions, we have found that the absence of xanthophylls leads to reduced oligomerization of photosystems I and II. This is remarkable because these complexes do not bind xanthophylls. Oligomerization is even more disturbed in crtH mutant cells, which show limited carotenoid synthesis; in these cells also the phycobilisomes are distorted despite the fact that these extramembranous light-harvesting complexes do not contain carotenoids. The number of phycocyanin rods connected to the phycobilisome core is strongly reduced leading to high amounts of unattached phycocyanin units. In the absence of carotenoids the overall organization of the thylakoid membranes is disturbed: Photosystem II is not formed, photosystem I hardly oligomerizes and the assembly of phycobilisomes remains incomplete. These data underline the importance of carotenoids in the structural and functional organization of the cyanobacterial photosynthetic machinery.

Genetic Modification of the Marine-Isolated Yeast Aureobasidium melanogenum P16 for Efficient Pullulan Production from Inulin.

In this study, in order to directly and efficiently convert inulin into pullulan, the INU1 gene from Kluyveromyces maximum KM was integrated into the genomic DNA and actively expressed in the high pullulan producer Aureobasidium melanogenum P16 isolated from the mangrove ecosystem. After the ability to produce pullulan from inulin by different transformants was examined, it was found that the recombinant strain EI36, one of the transformants, produced 40.92 U/ml of inulinase activity while its wild-type strain P16 only yielded 7.57 U/ml of inulinase activity. Most (99.27 %) of the inulinase produced by the recombinant strain EI36 was secreted into the culture. During the 10-l fermentation, 70.57 ± 1.3 g/l of pullulan in the fermented medium was attained from inulin (138.0 g/l) within 108 h, high inulinase activity (42.03 U/ml) was produced within 60 h, the added inulin was actively hydrolyzed by the secreted inulinase, and most of the reducing sugars were used by the recombinant strain EI36. This confirmed that the genetically engineered yeast of A. melanogenum strain P16 was suitable for direct pullulan production from inulin.

Optimal plant growth-promoting concentration of Azospirillum brasilense inoculated to cucumber, lettuce and tomato seeds varies between bacterial strains

Azospirillum brasilenseis a well-known plant growth-promoting rhizobacteria (PGPR) that can have positive impact on plant growth when present in sufficient density. The production of phytohormones byAzospirillumhas been proposed as one of the major mechanisms responsible for the observed plant growth effects. In particular, this plant growth-promoting effect could be mediated by IAA (indole-3-acetic acid), a phytohormone produced byAzospirillumin substantial amount, because the effect of inoculation with higher inoculum density on root morphology mimicked the increasing concentration of exogenous IAA applied to the seed. This study evaluated the effect of inoculation with different bacterial concentrations of threeA. brasilensestrains (Sp7, Sp7-S and Sp245) on the early seedling growth and endogenous plant IAA of cucumber, lettuce and tomato. Seeds were inoculated with 8, 7 and 6 log cfu ml−1of each strain before germinating in Petri dishes. The early seedling growth of vegetables was affected by the inoculation with theA. brasilensestrains. In cucumber, seeds inoculated with Sp7 at log 8 and 6 cfu ml−1, Sp7-S and Sp245 at log 8 and 7 increased seedling growth, vigor index and endogenous plant IAA by up to 55%. In lettuce, the inoculation with log 6 of Sp7, log 7 and 6 of Sp7-S, and log 8 and 7 of Sp245 yielded superior seedling growth with improved seedling vigor. In addition, log 7 and 8 of Sp7 and Sp7-S, respectively, increased IAA concentration by more than 20%. In tomato, Sp7 at log 6, Sp7-S and Sp245 at log 7 exerted more positive effects on root biomass. IAA concentrations increased up to 171% by inoculation with all concentrations of Sp7 and Sp7-S and more than 300% by Sp245 at log 8. The bacteria-elicited promotion of plant IAA production might improve plant function via effects on metabolism and morphology. These results demonstrate that seed inoculation with the strains at the studied range of cell concentrations stimulated early seedling development. However, the optimal promoting concentration varied between strains. Strain Sp7 appeared to be more beneficial at log 6 cfu ml−1while Sp7-S and Sp245 were more beneficial at log 7 or higher.

Improved potato microclonal reproduction with the plant growth-promoting rhizobacteria Azospirillum

Microclonal propagation in vitro is being actively used in the production of healthy planting material of food and ornamental plants. However, it needs further improvement to increase the growth rates of microclones in vitro and enhance regenerant survivability ex vitro. A promising approach to this end could be inoculating in vitro-micropropagated plants with plant growth-promoting rhizobacteria, specifically Azospirillum. However, the influence of Azospirillum inoculation on microclone behavior throughout the production process, including plant adaptation ex vitro and food crop productivity, has been underinvestigated. In this study, in vitro-growing potato (Solanum tuberosum L.) microclones were inoculated with Azospirillum brasilense strain Sp245. The microclones were then grown on in soil in the greenhouse and field, with the experiment lasting for 120 days. Root-associated bacteria were identified immunochemically, and the mitotic index of root meristematic cells was determined by a cytological method. The plant morphological parameters determined were shoot length, number of nodes per shoot, number of roots per plant, maximal root length, leaf area, percentage of surviving plants in the soil, and tuber yield and weight. Our results show that bacterial inoculation of potato microclones in vitro enhances plant adaptive capacity ex vitro and increases minituber yield. The percent survival index of field-grown inoculated plants was 1.5-fold greater than that of uninoculated plants. The overall tuber weight per plant was more than 30 % greater in the inoculated plants than it was in the control ones. For all cultivars on average, tuber yield per square meter increased by more than 45 % as a result of inoculation in vitro. This study is the first to report that Azospirillum inoculation of potato microclones not only improves the quality of planting material produced in vitro but also significantly increases minituber yield through enhancing plant adaptive capacity in the field.

Response of Cucumber Seedlings Fertilized with Fish Effluent to Azospirillum brasilense

ABSTRACTAn emphasis on reducing use of agrochemicals and recycling organic waste to alleviate pollution and nutrient discharge to the environment has prompted exploration of beneficial microbes and aquaculture wastewater in agriculture production. A study was conducted to investigate effects of strains Sp7, Sp7-S, and Sp245 of Azospirillum brasilense on cucumber (Cucumis sativus L.) seedlings fertilized with fish effluent. Cucumber seed were inoculated prior to germination and transplanting. Seedlings were grown in a greenhouse with natural light. Inoculated seedlings produced longer roots, greater root biomass, and higher total phosphorus, endogenous plant indole-3-acetic acid, and peroxidase activities. Inoculation caused small changes in the fish effluent bacterial community, indicating that these strains can be integrated into a production system utilizing fish effluent as a fertilizer. A. brasilense could be a valuable agent to help maximize the usefulness of aquaculture wastewater to support plant growth.

Microbial Degradation Mechanism and Pathway of the Novel Insecticide Paichongding by a Newly Isolated Sphingobacterium sp. P1-3 from Soil.

Using 1-((6-chloropydidin-3-yl)methyl)-7-methyl-8-nitro-5propoxy-1,2,3,5,6,7-hexahydroimidazo[1,2-α-]-pyridine (IPP) as the sole carbon source, we isolated a strain with a higher activity of IPP-degrading bacterium Sphingobacterium sp. P1-3 from soil. At 30 °C, pH 7.0 ,and 10 mg L(-1) IPP content, the degradation rate of IPP by Sphingobacterium sp. P1-3 could reach 57.75 and 62.47% in 20 and 30 days, respectively. The value of DT50 of IPP was 27 d at the level of 30 mg L(-1) IPP, while DT50 in the blank test was 151 d. During the IPP biodegradation process, five intermediates (M1-M5) were monitored and identified. On the basis of the identified metabolites and their biodegradation courses, a possible biodegradation pathway was proposed. IPP biodegradation mainly occurred on the tetrahydropyridine ring. IPP was transformed to five different metabolites by strain P1-3 through the oxidation and elimination of methyl, propyl, and nitro groups. Moreover, a new pathway involving M2 (1-((6-chloropydidin-3-yl)methyl)-7-methyl-8-hydroxy-5-propoxy-1,2,3,5,6,7-hexahydroimidazo [1,2-α-]-pyridine), M3 (1-((6-chloropydidin-3-yl)methyl)-7-methyl-5-carbonyl-1,2,3,5,6,7-hexahydroimidazo[1,2-α-]-pyridine), and M5 (8-amino-1,2,3,5,6,7-hexahydroimidazo[1,2-α-]-pyridine) was first monitored and identified.