Antimicrobial activity of FeIII,CuII, AgI,ZnII and HgII complexes of 2-(2-hydroxy-5-bromo/nitro-phenyl)-1H- and 2-(2-hydroxyphenyl)-5-methyl/chloro/nitro-1H-benzimidazoles

Antimicrobial activity of 2-(2-hydroxyphenyl)-5-R⁵-1H-benzimidazoles, 2-(2-hydroxy-5-R^5′-phenyl)-1H-benzimidazoles and their Fe^III, Cu^II, Ag^I, Zn^II and Hg^II nitrate complexes was tested towardStaphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri, andProteus mirabilis. Antifungal activity was tested againstCandida albicans. Benzimidazole benzene ring substituents increase the antimicrobial activity, phenol ring substituents decrease it. The ligands show an antibacterial effect against onlyS. aureus whereas Ag^I and Hg^II complexes of the ligands have a higher activity with respect to the other complexes to all the bacteria. On the other hand, Fe^III complexes show a considerable activity againstS. aureus andS. epidermidis.     

The pcsA gene from Streptomyces diastaticus var. 108 encodes a polyene carboxamide synthase with broad substrate specificity for polyene amides biosynthesis

Two structurally related polyene macrolides are produced by Streptomyces diastaticus var. 108: rimocidin (3a) and CE-108 (2a). Both bioactive metabolites are biosynthesized from the same pathway through type I polyketide synthases by choosing a starter unit either acetate or butyrate, resulting in 2a or 3a formation, respectively. Two additional polyene amides, CE-108B (2b) and rimocidin B (3b), are also produced “in vivo” when this strain was genetically modified by transformation with engineered SCP2*-derived vectors carrying the ermE gene. The two polyene amides, 2b and 3b, showed improved pharmacological properties, and are generated by a tailoring activity involved in the conversion of the exocyclic carboxylic group of 2a and 3a into their amide derivatives. The improvement on some biological properties of the resulting polyenes, compared with that of the parental compounds, encourages our interest for isolating the tailoring gene responsible for the polyene carboxamide biosynthesis, aimed to use it as tool for generating new bioactive compounds. In this work, we describe the isolation from S. diastaticus var. 108 the corresponding gene, pcsA, encoding a polyene carboxamide synthase, belonging to the Class II glutamine amidotransferases and responsible for “in vivo” and “in vitro” formation of CE-108B (2b) and rimocidin B (3b). The fermentation broth from S. diastaticus var. 108 engineered with the appropriate pcsA gene construction, showed the polyene amides to be the major bioactive compounds.     

Taxonomy,purification and chemical characterization of four bioactive compounds from new <Emphasis Type="Italic">Streptomyces</Emphasis> sp. TN256 strain

A new actinomycete strain designated TN256, producing antimicrobial activity against pathogenic bacteria and fungi, was isolated from a Tunisian Saharan soil. Morphological and chemical studies indicated that strain TN256 belonged to the genus Streptomyces. Analysis of the 16S rDNA sequence of strain TN256 showed a similarity level ranging between 99.79 and 97.8% within Streptomyces microflavus DSM 40331^T and Streptomyces griseorubiginosus DSM 40469^T respectively. The comparison of its physiological characteristics showed significant differences with the nearest species. Combined analysis of the 16 S rRNA gene sequences (FN687758), fatty acids profile, and results of physiological and biochemical tests indicated that there were genotypic and phenotypic differentiations of that isolate from other Streptomyces species neighbours. These date strongly suggest that strain TN256 represents a novel species with the type strain Streptomyces TN256 (=CTM50228^T). Experimental validation by DNA–DNA hybridization would be required for conclusive confirmation. Four active products (1–4) were isolated from the culture broth of Streptomyces TN256 using various separation and purification steps and procedures. 1: N-[2-(1H-indol-3-yl)-2 oxo-ethyl] acetamide ‘alkaloid’ derivative; 2: di-(2-ethylhexyl) phthalate, a phthalate derivative; 3: 1-Nonadecene and 4: Cyclo (l-Pro-l-Tyr) a diketopiperazine ‘DKP’ derivative. The chemical structure of these four active compounds was established on the basis of spectroscopic studies NMR and by comparing with data from the literature. According to our biological studies, we showed in this work that the pure compounds (1–4) possess antibacterial and antifungal activities.     

Antioxidant activity of 5-alkoxymethyl-6-chromanols

Abstract

The 5-alkoxymethyl-2,2,7,8-tetramethyl-6-chromanols (II) are excellent antioxidants against autoxidising safflower oil (ASO), although not as good as 2,2,5,7,8-pentamethyl-6-chromanol (I), the model compound of -tocopherol. The aim of this work was to determine whether the rate of reaction of (II) with the radicals diphenylpicrylhydrazyl (DPP^·) and galvinoxyl (ArO^·) was directly proportional to their antioxidant activity against ASO. Compounds (II) reacted faster with DPP^·. than with ArO^·. but, in each case, slower than compound (I). The rates of reaction of I and II with both radicals followed the order I > II (R = H) > II (R = CH₃) > II (R = other alkyls) and were directly proportional to their antioxidant activity against ASO.     

Isolation and partial characterization of antimicrobial compounds from a new strain <Emphasis Type="Italic">Nonomuraea</Emphasis> sp. NM94

An actinomycete strain NM94 was isolated from a Saharan soil sample by a dilution agar plating method using chitin-vitamins B medium supplemented with penicillin. The strain presented the morphological and chemical characteristics of the genus Nonomuraea. On the basis of 16S rDNA analysis and physiological tests, this isolate was found to be quite different from the known species of Nonomuraea and might be new. The strain NM94 secreted several antibiotics on yeast extract malt extract glucose medium that were active against some Gram-positive bacteria, yeast, and fungi. The antibiotics were extracted with dichloromethane and detected by bioautography on silica gel plates using Mucor ramannianus and Bacillus subtilis as the test organisms. Among these antibiotics, a complex called 94A showed interesting antifungal activity. It was selected and purified by reverse-phase HPLC. This complex was composed of five compounds. Spectroscopic studies by infrared, mass, and ¹H NMR of the compounds were carried out. Initial results showed that these molecules differed from the known antibiotics produced by other Nonomuraea species.     

Regioselective deglycosylation of onion quercetin glucosides by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Bioconversion of quercetin glucosides using four generally recognized as safe (GRAS) organisms (Aspergillus oryzae, Bacillus subtilis, Lactobacillus plantarum, and Saccharomyces cerevisiae) was evaluated by measuring changes in the levels of quercetin compounds of onion. Of the four organisms, S. cerevisiae increased the content of quercetin-3-O-β-d-glucoside (III; isoquercitrin) and quercetin (IV), whereas decreasing quercetin-3,4′-O-β-d-glucoside (I) and quercetin-4′-O-β-d-glucoside (II). Also, S. cerevisiae converted authentic compound I to III, and II to IV, respectively. These results suggest that S. cerevisiae can be used to increase the levels of isoquercitrin (III), the most bioavailable quercetin compound in onion.     

Interaction of the tylosin-resistance methyltransferase RlmA II at its rRNA target differs from the orthologue RlmA I

RlmA^II methylates the N1-position of nucleotide G748 in hairpin 35 of 23 S rRNA. The resultant methyl group extends into the peptide channel of the 50 S ribosomal subunit and confers resistance to tylosin and other mycinosylated macrolide antibiotics. Methylation at G748 occurs in several groups of Gram-positive bacteria, including the tylosin-producer Streptomyces fradiae and the pathogen Streptococcus pneumoniae. Recombinant S. pneumoniae RlmA^II was purified and shown to retain its activity and specificity in vitro when tested on unmethylated 23 S rRNA substrates. RlmA^II makes multiple footprint contacts with nucleotides in stem-loops 33, 34 and 35, and does not interact elsewhere in the rRNA. Binding of RlmA^II to the rRNA is dependent on the cofactor S-adenosylmethionine (or S-adenosylhomocysteine). RlmA^II interacts with the same rRNA region as the orthologous enzyme RlmA^I that methylates at nucleotide G745. Differences in nucleotide contacts within hairpin 35 indicate how the two methyltransferases recognize their distinct targets.     

Ordering selected Zn(II), Cu(II), Pd(II) and Co(III) complex compounds: their separately and combinedly antibacterial therapy and DNA-binding studies

Abstract

In this study, four Co(III)-, Cu(II)-, Zn(II)- and Pd(II)-based potent antibacterial complexes of formula K₃[Co(ox)₃]·3H₂O (I), [Cu(phen)₂Cl]Cl·6.5H₂O (II), [Zn(phen)₃]Cl₂ (III) and [Pd(phen)₂](NO₃)₂ (IV) (where ox is oxalato and phen is 1,10-phenanthroline) were synthesized. They were characterized by elemental analysis, molar conductivity measurements, UV–vis, Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (¹H-NMR) techniques. These metal complexes were ordered in three combination series of I+II, I+II+III and I+II+III+IV. Antibacterial screening for each metal complex and their combinations against Gram-positive and Gram-negative bacteria revealed that all compounds were more potent antibacterial agents against the Gram-negative than those of the Gram-positive bacteria. The four metal complexes showed antibacterial activity in the order I > II > III > IV, and the activity of their combinations followed the order of I+II+III+IV > I+II+III > I+II. The DNA-binding properties of complex (I) and its three combinations were studied using electronic absorption and fluorescence (ethidium bromide displacement assay) spectroscopy. The results obtained indicated that all series interact effectively with calf thymus DNA (CT-DNA). The binding constant (K_b), the number of binding sites (n) and the Stern–Volmer constant (K_sv) were obtained based on the results of fluorescence measurements. The calculated thermodynamic parameters supported that hydrogen bonding and van der Waals forces play a major role in the association of each series of metal complexes with CT-DNA and follow the above-binding affinity order for the series.

Communicated by Ramaswamy H. Sarma     

Study of the interaction between a histidine-deoxyguanosine hybrid and cisplatin

 A histidine-2′-deoxyguanosine hybrid, Phac-Hse(p^5′dG)-His-OH (I), was synthesized, and its reaction with cisplatin was monitored by reversed-phase HPLC and ¹H NMR. Two new compounds, II and III, were observed to be simultaneously formed, II in larger proportion than III. These products were isolated after HPLC purification and extensively characterized. Both II and III contained platinum, had the same mass and showed a bathochromic displacement of their absorption maxima with respect to that of I. Both remained undegraded upon enzymatic digestion and yielded I when treated with NaCN. From these data and the information provided by ¹H NMR analysis, we inferred that II and III were constitutional isomers, in particular chelates in which platinum was coordinated to the N7 of guanine and either the N^π or the N^τ imidazole nitrogens, respectively. No preference of the metal for either of these N-donors was observed. Received: 3 May 1999 / Accepted: 24 August 1999     

Simocyclinones: diversity of metabolites is dependent on fermentation conditions3

Simocyclinones, a novel group of angucyclinone antibiotics, are produced by Streptomyces antibioticus Tü 6040. The compounds show antibacterial and antitumor properties. In submerged cultivation, the production of simocyclinones is strongly dependent on the carbon and nitrogen sources used in a chemically defined medium. Productivity of distinct components and diversity of simocyclinone compounds are influenced by the medium composition. Four series of simocyclinone compounds were detected by high-performance liquid chromatography (HPLC) diode array detector (DAD) and HPLC electrospray ionization (ESI) mass spectrometry (MS) analysis, isolated and the structures determined by nuclear magnetic resonance (NMR) techniques. Under optimized conditions, simocyclinone D8 was produced in an amount of 300 mg l⁻¹ and simocyclinone C4 in a concentration up to 50 mg l⁻¹. Journal of Industrial Microbiology & Biotechnology (2001) 27, 144–148. Received 21 September 1999/ Accepted in revised form 20 January 2000     

Potent inhibitory effects of benzyl and p-xylidine-bis dithiocarbamate sodium salts on activities of mushroom tyrosinase

A novel monofunctional benzyldithiocarbamate, C₆H₅CH₂NHCSSNa (I), and a bifunctional p-xylidine-bis(dithiocarbamate), NaSSCNHCH₂C₆H₄CH₂NHCSSNa (II), as sodium salts, were synthesized by reaction between p-xylylenediamine or benzylamine with CS₂ in the presence of NaOH. They were characterized by spectroscopic techniques such as ¹H NMR, IR, and elemental analysis. These water-soluble compounds were examined for their inhibition of both activities of mushroom tyrosinase (MT) from a commercial source of Agricus bisporus. l-3,4- Dihydroxyphenylalanine (L-DOPA) and l-tyrosine were used as natural substrates for the catecholase and cresolase enzyme reactions, respectively. Kinetic studies showed noncompetitive inhibition of I and mixed type inhibition of II on both activities of MT. The inhibition constant (K_I) of II was smaller than that of I. Raising the temperature from 27 to 37°C caused a decrease in K_I values of I and an increase in values of II. The binding process for inhibition of I was only entropy driven, which means that the predominant interaction in the active site of the enzyme is hydrophobic; meanwhile, the electrostatic interaction can be important for the inhibition of II due to the enthalpy driven binding process. Fluorescence studies showed a decrease of emission intensity without a shift of emission maximum in the presence of different concentrations of compounds. An extrinsic fluorescence study did not show any considerable change of the tertiary structure of MT. Probably, the conformation of inhibitor-bound MT is stable and inflexible compared with uninhibited MT.     

Nematicidal activity of fervenulin isolated from a nematicidal actinomycete, <Emphasis Type="Italic">Streptomyces</Emphasis> sp. CMU-MH021, on <Emphasis Type="Italic">Meloidogyne incognita</Emphasis>

An isolate of the actinomycete, Streptomyces sp. CMU-MH021 produced secondary metabolites that inhibited egg hatch and increased juvenile mortality of the root-knot nematode Meloidogyne incognita in vitro. 16S rDNA gene sequencing showed that the isolate sequence was 99% identical to Streptomyces roseoverticillatus. The culture filtrates form different culture media were tested for nematocidal activity. The maximal activity against M. incognita was obtained by using modified basal (MB) medium. The nematicidal assay-directed fractionation of the culture broth delivered fervenulin (1) and isocoumarin (2). Fervenulin, a low molecular weight compound, shows a broad range of biological activities. However, nematicidal activity of fervenulin was not previously reported. The nematicidal activity of fervenulin (1) was assessed using the broth microdilution technique. The lowest minimum inhibitory concentrations (MICs) of the compound against egg hatch of M. incognita was 30 μg/ml and juvenile mortality of M. incognita increasing was observed at 120 μg/ml. Moreover, at the concentration of 250 μg/ml fervenulin (1) showed killing effect on second-stage nematode juveniles of M. incognita up to 100% after incubation for 96 h. Isocoumarin (2), another bioactive compound produced by Streptomyces sp. CMU-MH021, showed weak nematicidal activity with M. incognita.     

Inhibitory effect of extracts from Brazilian medicinal plants on the adhesion of <Emphasis Type="Italic">Candida albicans</Emphasis> to buccal epithelial cells

Plants are known to produce a plethora of secondary metabolites which are recognized as a useful source of new drugs or drug leads. Extracts and fractions of Schinus terebinthifolius Raddi (Anacardiaceae), Piper regnellii C.D.C. (Piperaceae), Rumex acetosa L. (Polygonaceae), and Punica granatum L. (Punicaceae) were assessed for their antifungal activity against eight clinical isolates of C. albicans. They were also evaluated for their effect on the adhesion of these C. albicans isolates to buccal epithelial cells (BECs). The ethyl acetate fraction from the leaves of S. terebinthifolius showed promising activity, inhibiting the growth of three C. albicans isolates at 7.8 μg ml⁻¹ and significantly inhibiting their adhesion to BEC at 15 μg ml⁻¹ . In addition, this fraction did not show cytotoxic activity against murine macrophages. The results show the potential of the plant extracts studied as a source of new antifungal compounds. Further studies are necessary for isolation and characterization of the active compounds of these plants.     

Bioconversion of codeine to semi-synthetic opiate derivatives by the cyanobacterium <Emphasis Type="Italic">Nostoc muscorum</Emphasis>

Very limited studies have been done to investigate the algal biotransformation of codeine to its opioid derivatives. On the other hand, microalgae have been recently introduced as potential tools for green synthesis of various organic compounds. In the present work, the capability of biotransformation of codeine by a locally isolate strain of cyanobacterium, Nostoc muscorum, was evaluated. Incubation of the whole cells of Nostoc muscorum with codeine (I) under continuous light photoregime of 60 μmol photons/m²s at 25°C for 5 days gave rise to four transformation products. The bioproducts were separated by gas chromatography and identified as 6-acetylcodeine (II), oxycodone (III), norcodeine (IV), morphine (V) and based on their mass spectra. Observed modifications included O-demethylation, N-demethylation, C6-acetylation, C14-hydroxilation, Δ⁷-reduction, and C6-oxidation. The ability of N. muscorum to convert codeine to oxycodone (III) represents an uncommon pattern of codeine metabolism in microorganisms that may be of industrial importance.     

Antibacterial combination therapy using Co3+, Cu2+, Zn2+ and Pd2+ complexes: Their calf thymus DNA binding studies

Four Co(III)-, Cu(II)-, Zn(II)-, and Pd(II)-based potent antibacterial complexes of formula K₃[Co(ox)₃].3H₂O (I), [Cu(bpy)₂Cl]Cl.5H₂O (II), [Zn(bpy)₃]Cl₂ (III), and [Pd(bpy)₂](NO₃)₂ (IV) (where ox is oxalate and bpy is 2,2′-bipyridine) were synthesized. They were characterized by elemental analyses, molar conductance measurements, UV–Vis, FTIR, ¹H NMR, and ¹³C NMR spectra. These metal complexes were ordered in three combination series of I + II, I + II + III, and I + II + III + IV. Antibacterial activity was tested for each of these four metal complexes and their combinations against Gram-positive and Gram-negative bacteria. All compounds were more potent antibacterial agents against the Gram-negative than those of the Gram-positive bacteria. The four metal complexes showed antibacterial activity in the order I > II > III > IV and the activity of their combinations followed the order of I + II + III + IV > I + II + III > I + II. CT-DNA binding studies of complex I and its three combinations were carried out using UV–vis spectral titration, displacement of ethidium bromide (EB), and electrophoretic mobility assay. The results obtained from UV–vis studies indicated that all series interact effectively with CT-DNA. Fluorescence titration revealed that the complexes quench DNA-EB strongly through the static quenching procedures. The binding constant (K_b), the Stern–Volmer constant (K_sv), and the number of binding sites (n) were determined at different temperatures of 293, 300, and 310 K, respectively. The calculated thermodynamic parameters supported that hydrogen binding and Van der Waals forces play a major role in association of each series of metal complexes with CT-DNA and follow the above-binding affinity order for the series.     

Purification and characterization of thermostable pectate-lyases from a newly isolated thermophilic bacterium, Thermoanaerobacter italicus sp. nov.

A novel thermophilic spore-forming anaerobic microorganism (strain Ab9) able to grow on citrus pectin and polygalacturonic acid (pectate) was isolated from a thermal spa in Italy. The newly isolated strain grows optimally at 70°C with a growth rate of 0.23 h⁻¹ with pectin and 0.12 h⁻¹ with pectate as substrates. Xylan, starch, and glycogen are also utilized as carbon sources and thermoactive xylanolytic (highest activity at 70°–75°C), amylolytic as well as pullulolytic enzymes (highest activity at 80°–85°C) are formed. Two thermoactive pectate lyases were isolated from the supernatant of a 300-l culture of isolate Ab9 after growth on citrus pectin. The two enzymes (lyases a and b) were purified to homogeneity by ammonium sulfate treatment, anion exchange chromatography, hydrophobic chromatography and finally by preparative gel electrophoresis. After sodium dodecylsulfate (SDS) gel electrophoresis, lyase a appeared as a single polypeptide with a molecular mass of 135 000 Da whereas lyase b consisted of two subunits with molecular masses of 93 000 Da and 158 000 Da. Both enzymes displayed similar catalytic properties with optimal activity at pH 9.0 and 80°C. The enzymes were very stable at 70°C and at 80°C with a half-life of more than 60 min. The maximal activity of the purified lyases was observed with orange pectate (100%) and pectate-sodium salt (90%), whereas pectin was attacked to a much lesser extent (50%). The K _m values of both lyases for pectate and citrus pectin were 0.5 g·l⁻¹ and 5.0 g·l⁻¹, respectively. After incubation with polygalacturonic acid, mono-, di-, and tri-galacturonate were detected as final products. A 2.5-fold increase of activity was obtained when pectate lyases were incubated in the presence of 1 mM Ca²⁺. The addition of 1 mM ethylenediaminetetraacetic acid (EDTA) resulted in complete inhibition of the enzymes. These heat-stable enzymes represent the first pectate-lyases isolated and characterized from a thermophilic anaerobic bacterium. On the basis of the results of the 16S rRNA sequence comparisons and the observed phenotypic differences, we propose strain Ab9 as a new species of Thermoanaerobacter, namely Thermoanaerobacter italicus sp. nov. Received: May 25, 1997 / Accepted: June 5, 1997     

Metal-based sulfonamides: Their preparation,characterization and in-vitro antibacterial,antifungal & cytotoxic properties. X-ray structure of 4-[(2-hydroxybenzylidene) amino] benzenesulfonamide

Synthesis, characterization and biological studies of Schiff base-derived sulfonamides and their Co (II), Cu (II), Ni (II) and Zn (II) complexes have been reported and screened for in-vitro antibacterial activity against six Gram-negative; E. coli, K. pneumoniae, P. aeruginosa, P. mirabilis, S. typhi and S. dysenteriae and four Gram-positive; B. cereus, C. diphtheriae, S. aureus and S. pyogenes bacterial strains and for in-vitro antifungal activity against T. longifusus, C. albicans, A. flavus, M. canis, F. solani, and C. glaberata. All compounds showed moderate to significant antibacterial activity, however, the zinc (II) complexes were found to be more active. Some of the compounds also showed significant antifungal activity against various fungal strains. Only compounds (6) and (10) displayed potent cytotoxic activity with LD₅₀ = 4.644 × 10^{? 4} and 4.106 × 10^{? 4} moles/mL respectively, against Artemia salina. The X-ray structure of 4-[(2-hydroxybenzylidene)amino]benzenesulfonamide is also reported.     

Amide derivatives with pyrazole carboxylic acids of 5-amino-1,3,4-thiadiazole 2-sulfonamide as new carbonic anhydrase inhibitors: Synthesis and investigation of inhibitory effects

Pyrazole carboxylic acid amides of 5-amino-1,3,4-thiadiazole-2-sulfonamide were synthesized from 4-benzoyl-1,5-diphenyl-1H-pyrazole-3-carbonyl chloride and 4-benzoyl-1-(3-nitrophenyl)-5-phenyl-1H-pyrazole-3-carbonyl chloride. Carbonic anhydrase isoenzymes (hCA-I and hCA-II) were purified from human erythrocyte cells by the affinity chromatography method. The inhibitory effects of 5-amino-1,3,4-thiadiazole-2-sulfonamide 1, acetazolamide 2 and new synthesized amides on these isozymes have been studied in vitro. The I₅₀ concentrations (the concentration of inhibitor producing a 50% inhibition of CA activity) against hydratase activity ranged from 1.2 to 2.2 nM for hCA-I and from 0.4 to 2 nM for hCA-II. The I₅₀ values against esterase activity ranged from 1.4 to 8 nM for hCA-I and from 1.3 to 6 nM for hCA-II. The K_i values were observed between 8.2·10^{? 5} to 6.2·10^{? 4} M for hCA-I and between 2.9·10^{? 4} to 8.2·10^{? 4} M for hCA-II. The comparison of new synthesized amides to 5-amino-1,3,4-thiadiazole-2-sulfonamide 1, acetazolamide 2 indicated that the new synthesized compounds (18–23) inhibit CA activity more potently than the parent compounds.     

Occurrence and antagonistic potential of Stenotrophomonas strains isolated from deep-sea invertebrates

Stenotrophomonas maltophilia is known to be of significance as opportunistic pathogen as well as a source of biocontrol and bioremediation activities. S. maltophilia strains have been isolated from rhizospheres, soil, clinical material, aquatic habitats, but little is known about Stenotrophomonas strains recovered from marine environments. During a survey of the biodiversity of Pseudomonas-like bacteria associated with deep-sea invertebrates six Stenotrophomonas strains were isolated from sponge, sea urchin, and ophiura specimens collected from differing Pacific areas, including the Philippine Sea, the Fiji Sea and the Bering Sea. 16S rRNA gene sequence analysis confirmed an assignment of marine isolates to the genus Stenotrophomonas as it placed four strains into the S. maltophilia CIP 60.77^T cluster and two related to the S. rhizophila DSM 14405^T. Together with a number of common characteristics typical of S. maltophilia and S. rhizophila marine isolates exhibited differences in pigmentation, a NaCl tolerance, a range of temperatures, which supported their growth, substrate utilization pattern, and antibiotics resistance. Strains displayed hemolytic and remarkable inhibitory activity against a number of fungal cultures and Gram-positive microorganisms, but very weak or none against Candida albicans. This is the first report on isolation, taxonomic characterization and antimicrobial activity of Stenotrophomonas strains isolated from deep-sea invertebrates.     

Antibacterial activity of <Emphasis Type="Italic">N</Emphasis>-benzylsalicylthioamides

The in-vitro biological activity of N-benzylsalicylthioamides against 8 bacterial strains was determined by broth microdilution method; results were compared with those obtained with neomycin, penicillin G, ciprofloxacin and penicillin V. The compounds showed moderate to high activity against G⁺ bacteria; especially compounds 4, 6, 13, 16–21 and 24 exhibited comparable or higher activity than reference drugs. The antibacterial activity was analyzed by quantitative structure-activity relationship (QSAR). The antibacterial activity increased with lipophilicity, with the presence of halogens and with increasing value of Hammet substituent constant σ.