Chemical composition and antibacterial potential of Artemisia arborescens L. essential oil

This study was undertaken to characterize the essential oil (EO) of Artemisia arborescens growing wild in Sicily. EO, extracted by steam distillation, was examined for its chemical composition and for its capability to inhibit some food-borne pathogen bacteria. A total of 43 compounds (13 monoterpene hydrocarbons, 14 oxygenated monoterpenes, 10 sesquiterpene hydrocarbons, three oxygenated sesquiterpenes and less amount of other three compounds), which account 93.73% of the total oil, were identified by gas chromatography and gas chromatography–mass spectrometry. Oxygenated monoterpenes (57.32%) constituted the main fraction, with β-thujone as the main compound (45.04%), followed by the sesquiterpene hydrocarbon chamazulene (22.71%). Undiluted EO showed a large inhibition spectrum against strains of Listeria monocytogenes (34 out of 44), whilst it was ineffective against enterobacteria and salmonellas. The minimum inhibition concentration (MIC) was evaluated for the two most sensitive strains (L. monocytogenes 186 and 7BO) at two cellular concentrations (10⁶ and 10⁷ CFU ml⁻¹). The lowest MIC (0.625 μl ml⁻¹, dilution of oil with acetone) was found for strain L. monocytogenes 186 at 10⁶ CFU ml⁻¹.     

Antimicrobial activity of crude extracts from mangrove fungal endophytes

The aim of this work was to select endophytic fungi from mangrove plants that produced antimicrobial substances. Minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) or minimal fungicidal concentrations (MFC) of crude extracts from 150 isolates were determined against potential human pathogens by a colorimetric microdilution method. Ninety-two isolates (61.3%) produced inhibitory compounds. Most of the extracts (28–32%) inhibited Staphylococcus aureus (MIC/MBC 4–200/64–200 μg ml⁻¹). Only two extracts inhibited Pseudomonas aeruginosa (MIC/MBC 200/>200 μg ml⁻¹). 25.5 and 11.7% inhibited Microsporum gypseum and Cryptococcus neoformans (MIC/MFC 4–200/8–200 μg ml⁻¹ and 8–200/8–200 μg ml⁻¹, respectively), while 7.5% were active against Candida albicans (MIC/MFC 32–200/32–200 μg ml⁻¹). None of the extracts inhibited Escherichia coli. The most active fungal extracts were from six genera, Acremonium, Diaporthe, Hypoxylon, Pestalotiopsis, Phomopsis, and Xylaria as identified using morphological and molecular methods. Phomopsis sp. MA194 (GU592007, GU592018) isolated from Rhizophora apiculata showed the broadest antimicrobial spectrum with low MIC values of 8–32 μg ml⁻¹against Gram-positive bacteria, yeasts and M. gypseum. It was concluded that endophytic fungi from mangrove plants are diverse, many produce compounds with antimicrobial activity and could be suitable sources of new antimicrobial natural products.     

Fungicidal Activity of Essential Oils from Cinnamomum cassia against the Pathogenic Fungi of Panax notoginseng Diseases

The frequent disease of Panax notoginseng caused by the pathogenic fungi in field cultivation has become the major threaten to the sustainable development of it. The present study was conducted to find natural agent with potential inhibition against pathogen. Therefore, the inhibitory effects of Cinnamomum cassia (L.) J.Presl essential oils (EOs) against P. notoginseng associated pathogenic fungi were conducted both in vitro and in vivo experiments. The results of the Oxford cup test revealed that C. cassia dry bark EO (50 mg/mL) had significant inhibitory activity on the growth of all tested fungi, and the growth of various pathogens was completely inhibited, except for that of Fusarium solani. Therefore, the constituents of C. cassia EOs were analyzed by GC/MS, and the research demonstrated that the main constituents of C. cassia dry bark EO were trans‐cinnamaldehyde (75.65 %), (E)‐2‐methoxycinnamaldehyde (6.08 %), cinnamaldehyde (3.47 %) and cinnamyl acetate (1.02 %). The MIC results showed that C. cassia dry bark EO and the main compounds had good antifungal effect on the tested strains, and the inhibitory effect was similar to that of hymexazol (chemical pesticide). By analyzing the value of the fraction inhibitory concentration index (FICI), additive effects, irrelevant effects and synergistic effects were observed after the mixture of hymexazol against various pathogens. Moreover, in vivo model showed that C. cassia dry bark EO could reduce the occurrence of anthrax in P. notoginseng. To widen the resources of C. cassia available, the compositions of both C. cassia fresh bark and leaf EOs were also tested and many common compositions existed among them. Taken together, it was concluded that C. cassia EO had the potential use in the field to reduce the pathogenic disease.     

Synergistic effect of green tea extract and probiotics on the pathogenic bacteria, <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> and <Emphasis Type="Italic">Streptococcus pyogenes</Emphasis>

The aim of this study was to assess the effect of a commercial green tea extract (TEAVIGO™) on the microbial growth of three probiotic strains (Lactobacillus and Bifidobacterium), as well as three pathogenic bacteria. MIC and co-culture studies were performed. The MICs of the green tea extract against Staphylococcus aureus and Streptococcus pyogenes (100 μg ml⁻¹) were considerably lower than those against the probiotic strains tested (>800 μg ml⁻¹) and Escherichia coli (800 μg ml⁻¹). In co-culture studies, a synergistic effect of the probiotic strains and the green tea extract was observed against both Staph. aureus and Strep. pyogenes. Green tea extract in combination with probiotics significantly reduced the viable count of both pathogens at 4 h and by 24 h had completely abolished the recovery of viable Staph. aureus and Strep. pyogenes. These reductions were more significant than the reductions induced by probiotics or green tea extracts used separately. These results demonstrate the potential for combined therapy using the green tea extract plus probiotics on microbial infections caused by Staph. aureus and Strep. pyogenes. As probiotics and the green tea extract are derived from natural products, treatment with these agents may represent important adjuncts to, or alternatives to, conventional antibiotic therapy.     

Bactericidal and antioxidant effects of essential oils from Satureja montana L., Myristica fragrans H. and Cymbopogon flexuosus

The extraction and characterization of the essential oils (EO) from Satureja montana L., Myristica fragrans H. and Cymbopogon flexuosus and the determination of their antibacterial and antioxidant activities were achieved. The EO were identified by gas chromatography/mass spectrometry and quantified by gas chromatography using a flame ionization detector. The antibacterial potential against Escherichia coli and Staphylococcus aureus was evaluated by cell susceptibility assays and by scanning electron microscopy. The antioxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl assay, by β-carotene bleaching and by determining the reducing power. Borneol (36·18%), γ-terpineol (12·66%) and carvacrol (11·07%) were the principal components in the EO from S. montana, and sabinene (49·23%) and α-pinene (13·81%) were found in the EO from M. fragrans. Geranial (59·66%) and neral (38·98%) isomers were the only major components in the EO from C. flexuosus. The EO from S. montana was effective against E. coli, with minimum inhibitory and bactericidal concentrations (MIC and MBC) of 6·25 µl ml⁻¹, whereas bactericidal potential against both was observed for the EO from M. fragrans; MIC = 6·25 µl ml⁻¹ for S. aureus and MBC = 12·5 µl ml⁻¹ for E. coli. A significant protective role on lipid substrates in the β-carotene bleaching assay was seen for the EO from S. montana and M. fragrans. Overall, such EO can be promising agents against pathogenic bacteria and for protecting biomolecules during oxidative stress.     

Potentiation of antifungal activity of terbinafine by dihydrojasmone and terpinolene against dermatophytes

Dermatophytoses are infections that affect keratinized tissues. Their main etiologic agents are fungi of the genera Microsporum and Trichophyton. The emergence of resistant fungi and the clinical relevance of dermatophytosis have encouraged studies that aim to increase the arsenal of drugs or act on mechanisms that confer multiple drug resistance. This study investigated the modulating activity of terbinafine promoted by dihydrojasmone and terpinolene against Microsporum canis LM 216, Trichophyton interdigitale H6 and T. interdigitale Δmdr2. The minimum inhibitory concentration (MIC) of test drugs was determined by broth microdilution. The effect of the drugs tested on plasma membrane functionality was analysed. Terbinafine MIC was determined in sub-inhibitory concentrations of monoterpenes. Finally, it was performed an association study with terbinafine and monoterpenes. Dihydrojasmone presented lower MIC values than terpinolene. All fungi were sensitive to terbinafine, starting at 1 μg ml⁻¹. All tested drugs increased K⁺ release (P < 0·05), affecting the functionality of the plasma membrane. Dihydrojasmone modulated the sensitivity of all strains against terbinafine, and terpinolene modulated the sensitivity of M. canis LM 216 and T. interdigitale Δmdr2. The monoterpenes and terbinafine drug associations presented synergism. In conclusion, the results suggest that the dihydrojasmone and terpinolene are promising antifungal agents that potentiate the antifungal activity of terbinafine against dermatophytes.     

Artemisia arborescens Essential Oil Composition,Enantiomeric Distribution,and Antimicrobial Activity from Different Wild Populations from the Mediterranean Area

Aerial parts of Artemisia arborescens were collected from different sites of the Mediterranean area (southwestern Algeria and southern Italy) and the chemical composition of their essential oil (EO) extracted by hydrodistillation was studied by both gas chromatography (GC) equipped with an enantioselective capillary column and GC/mass spectrometry (GC/MS). The EOs obtained were tested against several Listeria monocytogenes strains. Using GC and GC/MS, 41 compounds were identified, accounting for 96.0 – 98.8% of the total EO. All EOs showed a similar terpene profile, which was rich in chamazulene, β‐thujone, and camphor. However, the concentration of such compounds varied among the EOs. A. arborescens EO inhibited up to 83.3% of the L. monocytogenes strains, but the inhibitory spectrum varied among the EOs, with those from Algeria showing a higher inhibition degree than the Italian EOs. Such effect likely depended on the ketone (β‐thujone + camphor) content of the EO. The differences in the EO composition support the hypothesis that A. arborescens has at least two different chemotypes: a β‐thujone and a chamazulene type. The EO inhibitory spectrum indicates the A. arborescens EO as a valuable option in the control of the food‐borne pathogens.     

Development of quinolone resistance and prevalence of different virulence genes among Shigella flexneri and Shigella dysenteriae in environmental water samples

The purpose of this study was to find out the mechanism of quinolone resistance in Shigella sp. isolated from environmental water samples from various parts of Kolkata, India. Out of 196 Shigella sp. isolated from 2014 to 2017, we selected 32 Shigella isolates for antimicrobial susceptibility tests. The minimum inhibitory concentrations (MIC) for quinolones ranged from 30 to 50 μg ml⁻¹ for ofloxacin, 5–20 μg ml⁻¹ for ciprofloxacin and 20–30 μg ml⁻¹ for norfloxacin. A few amino acid changes were found in quinolone resistance determining region (QRDR) of gyrA. Mutations in gyrA lead to a higher increment of MIC of quinolones. Among the plasmid-mediated (PMQR) quinolone resistance genes investigated, qnrB and aac(6')-lb-cr genes were found in all isolates. qnrA and qnrS were found in 25% and 62% of the isolates, respectively. ipaH gene was found in all of the isolates followed by the presence of other virulence genes ial, sen and stx1. Almost all the isolates having high MICs showed efflux pump activity in drug accumulation assay. All the mechanisms may or may not be present in a single strain. Several types of efflux pumps, presence of PMQR genes and mutations in drug target site of QRDR region may play the crucial role for resistance in our isolates.     

Synthesis of benzoylthiourea derivatives and analysis of their antibacterial performance against planktonic Staphylococcus aureus and its biofilms

Following the appearance of several antimicrobial agents to control the spread of infections, two major challenges have emerged: (i) the occurrence and blowout of multiresistant bacteria and the increase of chronic diseases and (ii) difficult-to-eradicate infections. In this study, we tested five benzoylthiourea derivatives for their ability to inhibit and stop bacterial growth and evaluated the possible influence of 1,2,4-triazolyl-benzoylthiourea derivative 4 on the formation and eradication of Staphylococcus aureus biofilms. Benzoylthiourea derivatives 4 , 6 , 10 , 11 and 13 were obtained in one or two steps with low cost and subjected to tests to identify their minimum inhibitory concentration (MIC) and minimum bactericidal concentration. In vitro tests were also performed to assess their effects on biofilm formation and in preformed biofilms and scanning electron microscopy was used to visualize the effects on biofilm formation. The 1,2,4-triazolyl-benzoylthiourea derivative 4 showed bacteriostatic activity against the S. aureus HU25 clinical strain with an MIC of 16 µg ml⁻¹, which is below the toxic concentration (at 2500 µg ml⁻¹, 62·25% of the cells remained viable). Compound 4 also effectively prevented biofilm formation at the three subinhibitory concentrations tested (1/2 MIC, 1/4 MIC and 1/8 MIC) as confirmed by scanning electron microscopy. For breakdown of formed biofilms, the main influence was at a subinhibitory concentration (1/2 MIC). These findings make compound 4 a strong candidate for studies on the development of new antimicrobial and antibiofilm agents.     

Insights into collateral susceptibility and collateral resistance in Acinetobacter baumannii during antimicrobial adaptation

The susceptibility of Acinetobacter baumannii exposed to primary antibiotic can be either increased or decreased when exposed to secondary antibiotic. This study was designed to assess the relative fitness, collateral susceptibility and collateral resistance of polymyxin B- (PMB-) adapted A. baumannii to ciprofloxacin (CIP), meropenem (MER), PMB, tetracycline (TET) and tobramycin (TOB). Strains of wild-type A. baumannii KACC 12454 (AB^KACC), wild-type A. baumannii CCARM 12088 (AB^CCARM), PMB-adapted AB^KACC, PMB-adapted AB^CCARM, stabilized AB^KACC and stabilized AB^CCARM were used in this study. Compared to the wild-type AB^KACC, the MICs of PMB were increased from 2 to 128 μg ml⁻¹ against PMB-adapted AB^KACC, while MICs of CIP, MER, TET and TOB were decreased from 2 to 1 μg ml⁻¹, 16 to 1 μg ml⁻¹, 16 to 2 μg ml⁻¹ and 64 to 16 μg ml⁻¹, respectively. The PMB-adapted AB^CCARM was resistant to CIP (32 μg ml⁻¹) and PMB (64 μg ml⁻¹) compared to the wild-type AB^CCARM. The resistance of stabilized AB^KACC and AB^CCARM to all antibiotics was lost after antibiotic-free culture in the exception of CIP and TET. The susceptibilities of wild-type, PMB-adapted and stabilized AB^KACC and AB^CCARM to CIP, MER, PMB, TET and TOB were increased in the presence of β-lactamase and efflux pump inhibitors. The high levels of relative fitness were observed for stabilized AB^KACC, PMB-adapted AB^CCARM and stabilized AB^CCARM. The stabilized AB^KACC and PMB-adapted AB^CCARM were highly heteroresistance to PMB and TET, respectively. The PMB-adapted AB^KACC and AB^CCARM showed various antibiotic patterns, known as collateral susceptibility and collateral resistance. The results provide useful information for designing effective antibiotic regimens that can enhance the antibiotic activity against A. baumannii infections.     

In vitro assays on the susceptibility of four species of nematophagous fungi to anthelmintics and chemical fungicides/antifungal drug

Using nematophagous fungi for the biological control of animal parasitic nematodes will become one of the most promising strategies in the search for alternative chemical drugs. The purpose of this study was to check the in vitro activity of four anthelmintics, four chemical fungicides and two antifungal drugs on the spore germination of nematophagous fungi: Duddingtonia flagrans (SF170), Arthrobotrys oligospora (447), Arthrobotrys superba (435) and Arthrobotrys sp. (PS011). A modified 24-well cell culture plate assay was conducted to evaluate the susceptibility of nematophagous fungi against drugs tested by calculating the effective middle concentrations (EC₅₀) of each tested drug to inhibit the germination of fungal spores. EC₅₀ ranged between 0·7 and 47·2 μg ml⁻¹ for fenbendazole, thiabendazole and ivermectin, except levamisole (546·5–4057·8 μg ml⁻¹). EC₅₀ of tested fungicides was 0·6–2·3 μg ml⁻¹ for carbendazim, 55·9–247·4 μg ml⁻¹ for metalaxyl, 24·4–45·2 μg ml⁻¹ for difenoconazole, and 555·9–1438·3 μg ml⁻¹ for pentachloronitrobenzene (PCNB). EC₅₀ of two antifungal drugs was 0·03–3·4 μg ml⁻¹ for amphotericin B and 0·3–10·9 μg ml⁻¹ for ketoconazole. The results showed that 10 tested drugs, except for levamisole and PCNB, had in vitro inhibitory effects on nematophagous fungi. The chlamydospores of D. flagrans had the highest sensitivity to nine tested drugs, except for ketoconazole.     

Antifungal activities of anise oil, lime oil, and tangerine oil against molds on rubberwood (Hevea brasiliensis)

The antifungal activities of anise oil, lime oil, and tangerine oil against molds identified from rubberwood surfaces (Aspergillus niger, Penicillium chrysogenum, and Penicillium sp.) were investigated. The broth dilution method was employed to determine the minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) using the concentration of essential oils between 20 and 200 μl ml⁻¹. Inhibitory effects of the essential oils against those molds on rubberwood were also examined by means of the dip treatment and vacuum impregnation treatment. It was found that the MIC and MFC values for each treatment on agar were identical for all conditions examined. Anise oil was the strongest inhibitor with the MIC and MFC of 40 μl ml⁻¹ against Penicillium sp. and A. niger, and 60 μl ml⁻¹ against P. chrysogenum. Lime oil and tangerine oil were also effective against those molds at higher concentrations of 100–180 μl ml⁻¹. All essential oils at the MIC and MFC provided a protection from mold growth on rubberwood for at least 12 weeks at storage conditions of 30 °C with 100% RH.     

Heteroresistance to the model antimicrobial peptide polymyxin B in the emerging Neisseria meningitidis lineage 11.2 urethritis clade: mutations in the pilMNOPQ operon

Clusters of Neisseria meningitidis (Nm) urethritis among primarily heterosexual males in multiple US cities have been attributed to a unique non‐encapsulated meningococcal clade (the US Nm urethritis clade, US_NmUC) within the hypervirulent clonal complex 11. Resistance to antimicrobial peptides (AMPs) is a key feature of urogenital pathogenesis of the closely related species, Neisseria gonorrhoeae. The US_NmUC isolates were found to be highly resistant to the model AMP, polymyxin B (PmB, MICs 64–256 µg ml^–1). The isolates also demonstrated stable subpopulations of heteroresistant colonies that showed near total resistant to PmB (MICs 384–1024 µg ml^–1) and colistin (MIC 256 µg ml^–1) as well as enhanced LL‐37 resistance. This is the first observation of heteroresistance in N. meningitidis. Consistent with previous findings, overall PmB resistance in US_NmUC isolates was due to active Mtr efflux and LptA‐mediated lipid A modification. However, whole genome sequencing, variant analyses and directed mutagenesis revealed that the heteroresistance phenotypes and very high‐level AMP resistance were the result of point mutations and IS1655 element movement in the pilMNOPQ operon, encoding the type IV pilin biogenesis apparatus. Cross‐resistance to other classes of antibiotics was also observed in the heteroresistant colonies. High‐level resistance to AMPs may contribute to the pathogenesis of US_NmUC.     

Optimization of Antifungal Effect of Surfactin and Iturin to <Emphasis Type="Italic">Penicillium notatum</Emphasis> in Syrup of Peach by RSM

In the paper, the sensitivity of Penicillium notatum to surfactin and iturin was determined, and the optimization of the antifungal of surfactin and iturin to Penicillium notatum in syrup of peach by a response surface methodology (RSM) was researched. Results demonstrated that Penicillium notatum was sensitive to them, whose minimal inhibitory concentration (MIC) was 62.5 and 31.25 μg ml⁻¹ respectively. In the optimization experiment, when the temperature was 2.37°C, the action time was 25.21 h, and the concentration (surfactin/iturin weight ratio 1:1) was 40.26 μg ml⁻¹, Penicillium notatum could be sterilized by 5 orders of magnitude. All the results in the experiment indicated surfactin and iturin could kill remarkably Penicillium notatum in syrup of peach.     

Antifungal activity of streptavidin C1 and C2 against pathogens causing Fusarium wilt

Fusarium wilt is caused by the soil-inhabiting fungus Fusarium oxysporum ff. spp. and is one of the most devastating plant diseases, resulting in losses and decreasing the quality and safety of agricultural crops. We recently reported the structures and biochemical properties of two biotin-binding proteins, streptavidin C1 and C2 (isolated from Streptomyces cinnamonensis strain KPP02129). In the present study, the potential of the biotin-binding proteins as antifungal agent for Fusarium wilt pathogens was investigated using recombinant streptavidin C1 and C2. The minimum inhibitory concentration of streptavidin C2 was found to be 16 µg ml^–1 for inhibiting the mycelial growth of F. oxysporum f.sp. cucumerinum and F. oxysporum f.sp. lycopersici, while that of streptavidin C1 was found to be 64 µg ml^–1. Compared with the nontreated control soil, the population density of F. oxysporum f.sp. lycopersici in the soil was reduced to 49·5% and 39·6% on treatment with streptavidin C1 (500 µg ml^–1) and C2 (500 µg ml^–1), respectively. A greenhouse experiment revealed that Fusarium wilt of tomato plants was completely inhibited on soil drenching using a 50-ml culture filtrate of the streptavidin-producing strain KPP02129.     

Novel strategies of essential oils,chitosan, and nano- chitosan for inhibition of multi-drug resistant: E. coli O157:H7 and Listeria monocytogenes

Despite the wide range of available antibiotics, food borne bacteria demonstrate a huge spectrum of resistance. The current study aims to use natural components such as essential oils (EOs), chitosan, and nano-chitosan that have very influential antibacterial properties with novel technologies like chitosan solution/film loaded with EOs against multi-drug resistant bacteria. Two strains of Escherichia coli O157:H7 and three strains of Listeria monocytogenes were used to estimate antibiotics resistance. Ten EOs and their mixture, chitosan, nano-chitosan, chitosan plus EO solutions, and biodegradable chitosan film enriched with EOs were tested as antibacterial agents against pathogenic bacterial strains. Results showed that E. coli O157:H7 51,659 and L. monocytogenes 19,116 relatively exhibited considerable resistance to more than one single antibiotic. Turmeric, cumin, pepper black, and marjoram did not show any inhibition zone against L. monocytogenes; Whereas, clove, thyme, cinnamon, and garlic EOs exhibited high antibacterial activity against L. monocytogenes with minimum inhibitory concentration (MIC) of 250–400 μl 100^?1 ml and against E. coli O157:H7 with an MIC of 350–500 μl 100^?1 ml, respectively. Among combinations, clove, and thyme EOs showed the highest antibacterial activity against E. coli O157:H7 with MIC of 170 μl 100^?1 ml, and the combination of cinnamon and clove EOs showed the strongest antibacterial activity against L. monocytogenes with an MIC of 120 μl 100^?1 ml. Both chitosan and nano-chitosan showed a promising potential as an antibacterial agent against pathogenic bacteria as their MICs were relatively lower against L. monocytogenes than for E. coli O157:H7. Chitosan combined with each of cinnamon, clove, and thyme oil have a more effective antibacterial activity against L. monocytogenes and E. coli O157:H7 than the mixture of oils alone. Furthermore, the use of either chitosan solution or biodegradable chitosan film loaded with a combination of clove and thyme EOs had the strongest antibacterial activity against L. monocytogenes and E. coli O157:H7. However, chitosan film without EOs did not exhibit an inhibition zone against the tested bacterial strains.     

Termiticidal activity of lectins from Myracrodruon urundeuva against Nasutitermes corniger and its mechanisms

The isolation of lectins from Myracrodruon urundeuva bark (MuBL) and heartwood (MuHL) as well as the termiticidal activity of MuHL against Nasutitermes corniger has already been described. This work reports on the purification of a leaf lectin (MuLL) and the characterization of MuBL, MuHL, and MuLL; also described are the resistance of hemagglutinating activity of the three lectins to trypsin activity from N. corniger gut and the termiticidal activity on N. corniger of MuBL (LC₅₀ of 0.974 mg ml⁻¹ on workers and 0.787 mg ml⁻¹ on soldiers) and MuLL (LC₅₀ of 0.374 mg ml⁻¹ on workers and 0.432 mg ml⁻¹ on soldiers). The antibacterial effect of MuBL, MuHL, and MuLL on bacteria from gut of N. corniger was also investigated and lectins showed similar bacteriostatic activity (MIC of 62.5 ??g ml⁻¹ for workers and 125 ??g ml⁻¹ for soldiers). MuBL and MuHL were more efficient bactericidal agents on bacteria in the workers’ gut (MBC of 125 ??g ml⁻¹) than MuLL (MBC of 250 ??g ml⁻¹) and similar bactericidal activity was detected on bacteria in the gut of soldiers (MBC of 250 ??g ml⁻¹). The termiticidal activity of M. urundeuva lectins can be explained by the chitin-binding property, resistance to termite digestive enzyme, and the antibacterial effect on symbiotic bacteria of N. corniger gut.     

Isolation of antifouling compounds from the marine bacterium, <Emphasis Type="Italic">Shewanella oneidensis</Emphasis> SCH0402

Two compounds, 2-hydroxymyristic acid (HMA) and cis-9-oleic acid (COA), were isolated from a chloroform extract of the marine bacterium, Shewanella oneidensis SCH0402. In a spectrophotometer-based chemotaxis assay, HMA completely eliminated the optical density (OD) of Alteromonas marina SCH0401 and Bacillus atrophaeus SCH0408, motile, fouling bacteria, at 100 and 1000 μg ml⁻¹, respectively. COA similarly decreased the OD of A. marina and B. atrophaeus by 100% at 1000 μg ml⁻¹. The commercially available, highly toxic anti-fouling compound, tributyltin oxide (TBTO) never reduced the OD of the target bacteria by 100% even at higher concentration. Instead, all the test bacterial cells were killed at higher than 1000 μg ml⁻¹ of concentration. Both HMA and COA inhibited germination of Ulva pertusa spores completely at 10 and 100 μg ml⁻¹, respectively, while TBTO inhibited germination at 0.01 μg ml⁻¹. However, in field assays, both HMA and COA showed anti-fouling activities as potent as TBTO against a wide range of fouling organisms, including micro- and macro-algae, barnacles, and mussels. The average fouling coverage on the surface of the control panel was 93 ± 6% after 1.5 years but no fouling was observed on the surface of the test panel onto which each compound was applied separately. Thus, bacterial repellent compounds can be used as substitutes for potent toxic anti-fouling compounds, resulting in higher standards of environmental safety without loss of anti-fouling performance.     

Biodegradation of lindane pesticide by non white- rots soil fungus <Emphasis Type="Italic">Fusarium</Emphasis> sp.

Lindane or γ- hexachlorocyclohexane (γ-HCH) is a chlorinated pesticide and its toxic effects on biota necessitate its removal. Microbial degradation is an important process for pesticide bioremediation and the role of soil fungi in recycling of organic matter prompted us to study the biodegradation of lindane using fungi. This study aims at enrichment, isolation and screening of soil fungi capable of metabolizing lindane. Two Fusarium species (F. poae and F. solani) isolated from the pesticide contaminated soil showed better growth on the plates supplemented with lindane as a sole carbon source, when compared with the growth performance of other fungal isolates from the same contaminated soil. However, ANOVA revealed a significant difference in fungal biomass production in both F. poae (F = 22.02; N = 15; P < 0.001) and F. solani (F = 268.75; N = 15; P < 0.001) across different lindane concentrations (0–600 μg ml⁻¹). Growth of both Fusarium sp. was maximum at a lindane concentration of 100 μg ml⁻¹, while minimum at 600 μg ml⁻¹ concentrations. Results on the time dependent release of chlorine by the Fusarium strains in the presence of various concentration of lindane showed the highest mineralization of the pesticide on 10th day of incubation. Time dependent variations in the release of chlorine from 1st to 10th day by both the selected fungal strains were found to be statistically significant. A significant positive relationship exists between fungal biomass increase and chlorine release existed for both F. solani (R2 = 0.960) and F. poae (R2 = 0.628). The results of gas chromatograph analysis of γ- HCH confirmed the biodegradation and utilization of γ- HCH by F. poae and F. solani. The data on lindane degradation by the two fungal strains demonstrated that the biodegradation of lindane by F. solani (59.4%) was slightly higher than that by the F. poae (56.7%).     

Synergistic Impact of Phosphate Solubilizing Bacteria and Phosphorus Rates on Growth,Antioxidative Defense System,and Yield Characteristics of Upland Rice (Oryza sativa L.)

In the present study, we examined the synergistic effect of phosphate solubilizing bacteria (PSB) and the chemical phosphate on the growth, photosynthetic efficiency, phosphorus (P) uptake, antioxidant activity, and yield of upland rice. Three effective bacterial strains with potent P solubilizing activity viz., Bacillus licheniformis (688.18 µg ml^?1), Pantoea dispersa (570.90 µg ml^?1), and Staphylococcus sp. (551.81 µg ml^?1), were isolated from rice rhizosphere to study their impact on upland rice growth and yield under field conditions for two consecutive years. The experiment data revealed significant increments in shoot height, shoot dry weight, total chlorophyll, carotenoid, chlorophyll fluorescence (fv/fm), P uptake, antioxidant activity, and yield characteristics in upland rice treated with individual PSB or their consortia alone, compared to uninoculated control. However, the integrated use of PSB with 50% recommended P dose showed maximum increment in growth indices (21.25%, 21.86% increase in shoot length and 87.18%, 97.06% increase in shoot dry weight), P uptake (110.37%, 122.78% increase), and yield (50.58%, 35.64% increase) compared to uninoculated control for 2018 and 2019, respectively, indicating a reduction in the dependence of chemical P fertilizer by 50%. Therefore, it can be concluded that combined application of PSB and 50% recommended dose of chemical P can be implied for the sustainable cultivation of upland rice systems to give maximum benefits to the farmers and the environment.