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Proteases are a group of enzymes that catalyse the degradation of proteins resulting in the production of their amino acid constituents. In the present study newly isolated Streptomyces sp. was subjected to produce proteases through solid state fermentation while wheat bran was used as substrate. To produce proteases, a local strain Streptomyces sp. was isolated from a soil sample of Ezzemouls saltpan, located in Ain M'lila (East of Algeria). The phenotypic and phylogenetic studies of this strain showed that it represents probably a new species. The SSF production medium for Streptomyces sp. was optimized using Plackett and Burman statistical methods. The results showed a maximum activity on basal wheat bran medium supplemented with 1% fructose. The best SSF humidifying solution was pH 9.0 phosphate buffer at 50% moisture. Protease has an optimum at pH 7.0, which is a typical characteristic of neutral proteases. The optimum temperature was 60°C and proved stable up to 80°C. The results showed that the novel Streptomyces sp. isolate is a good producer of extracellular neutral protease on wheat bran, which can be beneficial for industries. J. Bio-Sci. 29(1): 33-48, 2021 (June)

In literature, it remains little explored the soil–plant relationships within Capsicum agroecosystem. We studied how chili peppers plants contribute to influence microbial diversity. Across the bul...

Mushroom compounds and biomolecules are known for their biological beneficial effects and dietary properties. Their molecules can be used in immunology for their ability to stimulate immune cells and in biotherapy of diseases. In this study, the immunomodulatory effect using carbon clearance test in vivo of partial purified lectin of Lactarius deliciosus using DEAE-Sephacyl column, with sugar affinity against galactose, methyl-β-D-galactopyranoside and lactose, showed a significant effect on phagocytic activity and half-life of carbon particles in mice with different concentrations (5, 10, 15, and 30 mg/kg). The results showed that the immunomodulatory effect increased in low doses and decreased in high doses compared with the control group p < 0.0001. L. deliciosus lectin exerted a dose-dependent immunostimulant activity toward the reticulo-endothelial system, and phagocytic activity toward macrophages and neutrophils in spleen and liver against the colloidal carbon.

Nigericin, one of the main ionophoric polyethers produced by various Streptomyces strains, presents relevant biological activities including antibacterial and recently studied antitumor properties. This work describes the influence of different culture conditions on the production of this metabolite by Streptomyces sp. SF10, isolated from a semi-arid soil sample collected at Chélia Mountain, in Khenchela (Northeastern Algeria) and identified as Streptomyces youssoufiensis. The extracts from the strain, cultured in a solid state or submerged fermentation conditions, using several carbon sources at different pH values, in the presence or absence of iron (II) sulfate and in co-culture with other Streptomyces species, were analyzed using a high-performance liquid chromatography (HPLC) system equipped with an evaporative light scattering detector (ELSD). The best culture conditions provided a concentration of nigericin of 0.490 ± 0.001 mg/mL in the extract. The HPLC-ELSD method, optimized here for the quantitative detection of nigericin, can find wider applications in the analysis of several other metabolites characterized by a similar polycyclic polyether structure or, more generally, by the lack of significant chromophores in their molecular structure.

International audience; Repeated application of pesticides disturbs microbial communities and cause dysfunctions on soil biological processes. Granstar® 75 DF is one of the most used sulfonylurea herbicides on cereal crops; it contains 75% of tribenuron-methyl. Assessing the changes on soil microbiota, particularly on the most abundant bacterial groups, will be a useful approach to determine the impact of Granstar® herbicide. For this purpose, we analyzed Actinobacteria, which are known for their diversity, abundance, and aptitude to resist to xenobiotic substances. Using a selective medium for Actinobacteria, 42 strains were isolated from both untreated and Granstar® treated soils. The number of isolates recovered from the treated agricultural soil was fewer than that isolated from the corresponding untreated soil, suggesting a negative effect of Granstar® herbicide on Actinobacteria community. Even so, the number of strains isolated from untreated and treated forest soil was quite similar. Among the isolates, resistant strains, tolerating high doses of Granstar® ranging from 0.3 to 0.6% (v/v), were obtained. The two most resistant strains (SRK12 and SRK17) were isolated from treated soils showing the importance of prior exposure to herbicides for bacterial adaptation. SRK12 and SRK17 strains showed different morphological features. The phylogenetic analysis, based on 16S rRNA gene sequencing, clustered the SRK12 strain with four Streptomyces type strains (S. vinaceusdrappus, S. mutabilis, S. ghanaensis and S. enissocaesilis), while SRK17 strain was closely related to Streptomyces africanus. Both strains were unable to grow on tribenuron methyl as unique source of carbon, despite its advanced dissipation. On the other hand, when glucose was added to tribenuron methyl, the bacterial development was evident with even an improvement of the tribenuron methyl degradation. In all cases, as tribenuron methyl disappeared, two compounds were detected with increased concentrations. These by-products appeared to be persistent and were not degraded either chemically or by the studied strains. Based on these observations, we suggested that bacterial activity on carbon substrates could be directly involved in the partial breakdown of tribenuron methyl, by generating the required acidity for the first step of the hydrolysis. Such a process would be interesting to consider in bioremediation of neutral and alkaline tribenuron methyl-polluted soils.

The present work describes the metabolites produced by a strain identified as Streptomyces youssoufiensis, whose secondary metabolites profile has not been studied so far. The crude ethyl acetate extract was analyzed by high performance liquid chromatography-electrospray ionization mass spectrometry, leading to the detection of the ionophoric polyethers nigericin, epinigericin, abierixin and the newly isolated grisorixin methyl ester. The presence of epimeric forms of nigericin/epinigericin and grisorixin/epigrisorixin has spurred density functional theory computational calculations. This analysis was able to provide the relative stability of the most favored epimers, setting the basis for general structural considerations applicable to several other polyethers. Both nigericin sodium salt and grisorixin methyl ester showed to affect glioblastoma stem cells proliferation in a dose-dependent manner, with a higher activity for the more lipophilic grisorixin methyl ester (GI50 values of 3.85 and 3.05 μM for VIPI and COMI human glioblastoma stem cells, respectively).

Lactic acid bacteria termed probiotics have preventive as well as curative effects on several types of diarrhoea of different aetiologies. The main objective of this study was to screen lactobacilli strains having probiotic traits, isolated from Algerian healthy children faeces on the purpose of using them further in children diarrheal illnesses. One hundred and twenty (120) lactic acid bacteria isolates were selected from faecal samples of healthy Algerian children aged between five and ten years. Gram positive rods and catalase negative bacteria (52 isolates) were screened, in vitro, for their probiotic potential properties including ability to survive in simulated gastro-intestinal conditions, adherence to Caco-2 cells and their antimicrobial activity. The results show that only five strains resisted in simulated gastric juice at pH 1.5 and pepsin. Four of them were resistant to simulated intestinal conditions at pH 8 and pancreatin and have a good adherence. In the end, three of them were retained as they display interesting probiotic profiles characterized by a strong antimicrobial effect against some intestinal pathogenic bacteria. They were identified by 16S rDNA sequencing as Lactobacillus plantarum F12, Lactobacillus brevis G6 and Lactobacillus paracasei B13. Key words: Probiotics, Lactobacillus, selection criteria, human origin.

Actinomycetes are an uncommon agent of human infections and its pathogenic factors are not known. The present study reports a rare case isolation of an actinomycete from a woman pleural fluid; the strain was identified by 16S rRNA gene sequence analysis. This strain was tested to produce an extracellular protease that hydrolysis gelatin, casein and hemoglobin on agar mediums. The purification of the enzyme was carried by ammonium sulfate precipitation, gel filtration and ion exchange chromatographies. The activity of protease was studied at different pH values and temperatures and in the presence of metallic ions and inhibitors. The molecular weight of the enzyme was determined by 12% Tricine SDS-polyacrylamide gel electrophoresis. The strain was identified as Streptomyces cinereoruber ssp. cinereoruber. Extracellular proteolytic enzyme was purified at 19.67 fold and a 3.0% recovery. The enzyme was characterized as having optimal activities at pH 11.0 and 50°C, it keeps more than 50% of activity at pH between 4.0 to 12.0 and it is thermostable at 30 and 40°C. Enzymatic activity is enhanced in the presence of metal ions and inhibited by EDTA and 1,10-phenanthroline. The molecular weight was 53 kDa. This study reports the first case isolation of Streptomyces cinereoruber ssp. cinereoruber from pleural fluid, the extracellular zinc-metalloprotease was proposed as candidate virulence factor.

Proteolytic activity of a Streptomyces sp. strain isolated from Ezzemoul saltpans (Algeria) was studied on agar milk at three concentrations. The phenotypic and phylogenetic studies of this strain show that it represents probably new specie. The fermentation is carried out on two different media, prepared at three pH values. The results showed the presence of an alkaline protease with optimal pH and temperature of 8 and 40°C, respectively. The enzyme is stable up to 90°C, having a residual activity of 79% after 90 min. The enzyme production media are optimized according to statistical methods while using two plans of experiences. The first corresponds to the matrixes of Plackett and Burman in N=16 experiences and N-1 factors, twelve are real and three errors. The second is the central composite design of Box and Wilson. The analysis of the results allowed the selection of two factors having a significant effect on the production of the enzyme (fructose and malt extract), then defining theirs optima (7 g/l of fructose and 12 g/l of malt extract). Key words: Protease, streptomyces, identification, fermentation, optimization.

The rhizosphere is a rich source of actinobacteria and some members of this bacterial group present strong abilities in the biocontrol of plant diseases. In the present study, 72 strains of actinobacteria were isolated from different rhizospheric semi-arid soils collected in Algeria. Their in vitro antagonistic activity was assayed toward the following plant pathogenic fungi: Verticillium dahliae, Fusarium culmorum, Drechslera teres, Microdochium nivale, Bipolaris sorokiniana, Botrytis fabae and Fusarium oxysporum. All isolates showed chitinolytic activity and six isolates (Lac1, Lac3, Vic8, Pin10, Pru14 and Pru16), which inhibited the growth of five or more of the fungi tested, were selected for further study. According to morphological and physiological characteristics, as well as phylogenetic analysis of 16S rRNA gene sequences, isolates Lac1, Lac3, Pru14 and Pru16 were identified as members of the genus Streptomyces, namely S. griseus, S. rochei, S. anulatus and S. champavatii, respectively. ...

Two extremely halophilic archaea, strains Al-5(T) and K-1, were isolated from Lake Tebenquiche (Atacama Saltern, Chile) and Ezzemoul sabkha (Algeria), respectively. Cells of the two strains were short-rod-shaped and Gram-negative; colonies were orange-pigmented. They grew optimally at 37-40 degrees C and pH 7.0-7.5 in the presence of 25 % (w/v) NaCl. Magnesium was not required. Polar lipid analysis revealed the presence of phosphatidylglycerol and phosphatidylglycerophosphate methyl ester, the absence of phosphatidylglycerosulfate, and the presence of sulfated diglycosyl diether and diether diglycosyl as the sole glycolipids. DNA G+C contents of strains Al-5(T) and K-1 were 52.4 and 52.9 mol% (T(m) method), respectively. 16S rRNA gene sequence comparison with database sequences showed that strains Al-5(T) and K-1 were most closely related to Halomicrobium mukohataei DSM 12286(T) (similarities of 97.5 and 96.9 %, respectively). DNA-DNA hybridization indicated that strains Al-5(T) and K-1 were members of a single species. However, DNA-DNA relatedness to Halomicrobium mukohataei was 55.7+/-2.5 %. A comparative analysis of phenotypic characteristics and DNA-DNA hybridization between the isolates and Halomicrobium mukohataei DSM 12286(T) supported the conclusion that Al-5(T) and K-1 represent a novel species within the genus Halomicrobium, for which the name Halomicrobium katesii sp. nov. is proposed. The type strain is Al-5(T) (=CECT 7257(T)=DSM 19301(T)).

Resume Sur un lot de cinquante-cinq souches d’actinomycetes isolees a partir d’echantillons de sol aride preleves dans la region de Biskra, dix souches a structure filamenteuse ont ete purifiees. L’activite antibacterienne de ces souches a ete recherchee par deux techniques de diffusion en gelose, vis-a-vis de cinq bacteries-tests (Escherichi coli, Pseudomonas aeruginosa, Bacillus cereus, Streptococcus faecalis et Staphylococcus aureus). Les dix souches d’actinomycetes ont presente une activite antibacterienne plus ou moins importante contre toutes les bacteries-tests utilisees. L’effet du milieu de culture sur la production d’antibacteriens par les dix souches d’actinomycetes a ete etudie sur cinq differents milieux de culture. Les souches cultivees sur le milieu GB ont donne les plus importantes activites contrairement au milieu ISP2 sur lequel une seule souche a produit des molecules actives contre les bacteries-test.

Forty microbial strains isolated from raw milk samples and black and green olives were grown in MP5 (mineral pectin 5) medium containing 0.5% lemon pectin. All strains synthesized an extracellular polygalacturonase. Rhodotorula sp. ONRh9 (0.44 U·mL–1) and Leuconostoc sp. LLn1 (0.16 U·mL–1), which had a more active poly galacturonase in MP5 medium, were studied in MAPG5 medium containing polygalacturonic acid. Highest biomass and polygalacturonase production by these two strains were observed for polygalacturonic acid concentrations of 10 g·L–1(Rhodotorula sp. ONRh9) and 5 g·L–1(Leuconostoc sp. LLn1) and for initial pH values of 6 (Rhodotorula sp. ONRh9) and 5.5 (Leuconostoc sp. LLn1). The two strains grown in fermenters in MAPG5 medium generated the following results: with controlled initial pH, Rhodotorula sp. produced maximum biomass (DO) and polygalacturonase (PG) after 20 h (DO, 3.86; PG, 0.24 U·mL–1) of growth, and this level was sustained until the end of the culture; Leuconostoc sp. LLn1 synthesized more cells and polygalacturonase between 4 h (DO, 1.80; PG, 0.17 U·mL–1) and 24 h (DO, 3.90; PG, 0.27 U·mL–1) of culture. With uncontrolled initial pH, the cultures produced maximum biomass and poly galacturonase after 20 h (DO, 3.30; PG, 0.26 U·mL–1) for Rhodotorula sp. ONRh9 and 10 h (DO, 2.84; PG, 0.17 U·mL–1) for Leuconostoc sp. LLn1.Key words: Leuconostoc, Rhodotorula, polygalacturonic acid, polygalacturonase, cell growth.[Journal translation]

A novel extremely halophilic archaeon was isolated from Ezzemoul sabkha, Algeria. The strain, designated 5.1T, was neutrophilic, motile and Gram-negative. At least 15 % (w/v) NaCl was required for growth. The isolate grew at pH 6.5–9.0, with optimum growth at pH 7.0–7.5. Mg2+ was required for growth. Polar lipids were C20C20 derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester, and phosphatidylglycerol sulfate and sulfated diglycosyl diether. The genomic DNA G+C content of strain 5.1T was 61.9 mol% (T m). Phylogenetic analysis based on comparison of 16S rRNA gene sequences revealed that strain 5.1T clustered with Halorubrum species. The results of DNA–DNA hybridization and biochemical tests allowed genotypic and phenotypic differentiation of strain 5.1T from other Halorubrum species. The name Halorubrum ezzemoulense sp. nov. (type strain 5.1T=CECT 7099T=DSM 17463T) is proposed.

Resume Dans le cadre de la recherche de nouveaux antibiotiques elabores par des actinomycetes originaires des milieux extremes, l’activite antibacterienne d’une souche d’actinomycete isolee d’eau de Sebkha de Ain Mlila a ete etudiee. Ses caracteres morphologiques et macromorphologiques sur milieu ISP2 + 0,5 % NaCl permettent de la rapprocher de l’un des genres, Kitasatosporia, Saccharopolyspora ou. Les molecules bioactives produites par cette souche et excretees dans le milieu de fermentation sont extraites par trois solvants de polarite differente, celles du mycelium sont retrouvees dans l’extrait methanolique. L’etude cinetique de la croissance et de la production de substances inhibitrices, realisee sur milieu ISP2 + 0,5 % NaCl (220 tr/ mn, 28°C), a revele que l’activite antibacterienne de la souche A4 est maximale au quatrieme jour dans le mycelium et au cinquieme jour dans l’extrait butanolique du surnageant. La technique chromatographique de Betina a revele la presence de trois types de molecules dans le surnageant : deux extraites par le butanol ; un troisieme type, n’appartenant a aucune des 5 classes d’antibiotiques selon la Classification de Betina, est retrouve dans l’extrait benzenique du surnageant. Cette technique laisse supposer que les deux activites presentes dans l’extrait butanolique du surnageant et celles du mycelium (deux types) sont des molecules qui, selon la classification de Betina sont apparentees aux macrolides. Ces molecules resistent dans le surnageant a differents pH (de 3 a 9), sont stables a 70 C et apres congelation (– 20C).

International audience; As part of a research program whose aim is to identify new antifungal metabolites from rare actinomycetes, three Saharan soils from south east Algeria were analyzed. Twenty-seven (27) strains of actinomycetes were isolated and tested for their antifungal activity. The soil from the region of Biskra gave the highest number of actinomycetes, i.e. 52% versus 18% and 30% for the soils from El-Oued and Ourgla, respectively. The results of this study showed the GLM medium to be the most favorable for the isolation of actinomycetes from these ecosystems, on its own providing 17 strains out of the total number of actinomycetes isolated. Two strains presented very important antifungal activity against most of the filamentous fungi and test yeasts used. Molecular identification by polymerase chain reaction using universal 16S rDNA primers allowed the two active strains to be classified in the genus Streptomyces.

International audience; Sulfonylurea herbicides are widely used on a wide range of crops to control weeds. Chevalier® OnePass herbicide is a sulfonylurea herbicide intensively used on cereal crops in Algeria. No information is yet available about the biodegradation of this herbicide or about its effect on the bacterial community of the soil. In this study, we collected an untreated soil sample, and another sample was collected 1 month after treatment with the herbicide. Using a high-resolution melting DNA technique, we have shown that treatment with Chevalier® OnePass herbicide only slightly changed the composition of the whole bacterial community. Two hundred fifty-nine macroscopically different clones were isolated from the untreated and treated soil under both aerobic and microaerobic conditions. The strains were identified by sequencing a conserved fragment of the 16S rRNA gene. The phylogenetic trees constructed using the sequencing results confirmed that the bacterial populations were similar in the two soil samples. Species belonging to the Lysinibacillus, Bacillus, Pseudomonas, and Paenibacillus genera were the most abundant species found. Surprisingly, we found that among ten strains isolated from the treated soil, only six were resistant to the herbicide. Furthermore, bacterial overlay experiments showed that only one resistant strain (related to Stenotrophomonas maltophilia) allowed all the sensitive strains tested to grow in the presence of the herbicide. The other resistant strains allowed only certain sensitive strains to grow. On the basis of these results, we propose that there must be several biodegradation pathways for this sulfonylurea herbicide.

Objectives Inhabitants of developing countries such as those in North Africa have experienced lifestyle changes that have increased the risk of cardiovascular disease. The aim of the Epidemiological Trial of Hypertension in North Africa (ETHNA) was to evaluate the prevalence and clinical profile of hypertension in a large sample of individuals in North Africa. Methods This was an international, multicentre, epidemiological, cross-sectional study conducted in patients consulting primary care physicians in Algeria, Tunisia and Morocco. Data were collected via a medical examination and questionnaire covering patient demographics, medical history and cardiovascular risk factors. Associations between hypertension and patient characteristics were determined using conventional parametric statistical tests. Results In total, 28,500 individuals attending primary care physicians participated in this study: 41.8% from Algeria, 37.6% from Morocco and 20.6% from Tunisia. Mean age was 49.2 ± 16.8 years. The total prevalence of hypertension was 45.4% [95% confidence interval (CI) 44.8-46.0]; 29.0% of patients with hypertension were newly detected at the study visit. When adjusted for age and sex, the overall prevalence of hypertension was 26.9% (95% CI 26.4-27.4). Overall, 88.0% of the patients with hypertension were receiving or were newly prescribed antihypertensives (history of hypertension, 91.2%; newly detected, 80.3%). Among patients with a history of hypertension receiving antihypertensives at the study visit, only 35.7% had controlled hypertension. Conclusion This study suggests that the prevalence of hypertension in North Africa is high. Hypertension may also be underdiagnosed and ineffectively treated. Greater awareness and improved management of hypertension and cardiovascular risks are needed in this region.

A draft genome sequence of Tsukamurella sp., an aerobic bacterium isolated from a human sputum specimen, is described here. A new virus or provirus, TPA4, was characterized.

The cellulolytic bacterial species present in the caecum and colon contents of conventionally reared mature mice did not become established in the digestive tract when inoculated to axenic mice, whatever the size of the inoculum or the cellulose content of the diet. The cellulolytic bacterium Eubacterium cellulosolvens SC 10 isolated from mouse digestive flora was unable to become established in the digestive tract of the axenic mice whatever the cellulose content of the diet; it requires a feed rich in cellulose and a highly diversified microflora.

In the young rabbit, the celluloytic population appeared in the cecum and colon microflora between 12 and 16 days after birth. It increased rapidly with age to stabilize at a level of about 107 bacteria a few days after weaning. In the adult animal the xylanolytic and pectinolytic populations established at levels between 109 and 1010 bacteria g−1. The colic and cecal populations were comparable in size. When the feed cellulose content rose from 11 to 17% (P/V), the cellulolytic population increased about tenfold, and the range of individual variations decreased. All the fibrolytic strains isolated were strictly anaerobic;Eubacterium cellulosolvens was the most frequently isolated cellulolytic species. The eight xylanolytic strains and the twelve pectinolytic strains identified were assigned to the speciesBacteroides ruminicola.

A novel moderately halophilic bacterium belonging to the genus Halomonas was isolated from brine samples collected from Ezzemoul sabkha in north-eastern Algeria. The cells of strain 5-3(T) were Gram-negative, rod-shaped and non-motile. The strain was catalase- and oxidase-positive and produced an exopolysaccharide. Growth occurred at NaCl concentrations of 5-25% (optimum at 7.5%), at 30-50 degrees C (optimum at 37-40 degrees C) and at pH 6.0-9.0 (optimum at pH 7.5). The major fatty acids were C(12:0) 3-OH, C(16:1)omega7c/iso-C(15:0) 2-OH, C(16:0), C(18:1)omega7c and C(19:0)omega8c cyclo. The G+C content of the genomic DNA was 57.0 mol% (T(m)). The affiliation of strain 5-3(T) with the genus Halomonas was confirmed by 16S rRNA gene sequence comparisons. The most closely related species was Halomonas halmophila, which showed a 16S rRNA gene sequence similarity of 99.7%. However, the level of DNA-DNA relatedness between the novel isolate and the related Halomonas species was less than 31.4%. On the basis of the data from this polyphasic study, strain 5-3(T) represents a novel species of the genus Halomonas, for which the name Halomonas sabkhae sp. nov. is proposed. The type strain is 5-3(T) (=CECT 7246(T)=DSM 19122(T)=LMG 24084(T)).

The structure of PbCa alloys undergoes progressive changes at room temperature. A study of the early stages of their aging by optical microscopy has not been accomplished because the time required to prepare the samples is too long. This article describes a preparation technique consisting of an electrolytic polishing step at a temperature of −50°C, followed by repeated chemical etching with appropriate reagents. The technique allowed us to examine the quenched structure, to pinpoint the sites of discontinuous transformation (grain boundaries, intragranular sites, and domain walls), and to follow the early stages of growth in the transformed area as well as subsequent development. Transformation areas appearing during slow cooling could be distinguished from those appearing after cooling. The results obtained using this technique corroborate evidence obtained by other methods for these transformations.

Because peptide deformylase (PDF) is essential for the initiation of translation in eubacteria but not in eukaryotes, it is a potentially interesting target for antibiotics. Computer simulation using docking software can be used to model protein-ligand interactions, and in this brief report we describe its use in optimizing the design in PDF-directed inhibitors. PDF was used as target for a set of five inhibitors with substantial structural differences. Docking results show that the compound 1BB2 (actinonin) binds with high affinity to the enzyme and produces the most stable complex, forming nine hydrogen bonds with the enzyme active site. Its binding energy is DeltaG = -31.880 kJ/mol. The modeling study shows that when the methyl group of 1BB2 is replaced with an amine group, the binding energy is increased to -35.316 kJ/mole. This enhancement is more marked (DeltaG = -41.141 kJ/mol) when the propyl group and the five-membered ring of 1BB2 are replaced by an amide group and a phenyl ring, respectively. We describe an attempt to design better antibiotics on the basis of a computer-aided simulation of the interaction between a drug and its target molecule.

Forty microbial strains isolated from raw milk samples and black and green olives were grown in MP5 (mineral pectin 5) medium containing 0.5% lemon pectin. All strains synthesized an extracellular polygalacturonase. Rhodotorula sp. ONRh9 (0.44 U x mL(-1)) and Leuconostoc sp. LLn1 (0.16 U x mL(-1)), which had a more active polygalacturonase in MP5 medium, were studied in MAPG5 medium containing polygalacturonic acid. Highest biomass and polygalacturonase production by these two strains were observed for polygalacturonic acid concentrations of 10 g x L(-1) (Rhodotorula sp. ONRh9) and 5 g x L(-1) (Leuconostoc sp. LLn1) and for initial pH values of 6 (Rhodotorula sp. ONRh9) and 5.5 (Leuconostoc sp. LLn1). The two strains grown in fermenters in MAPG5 medium generated the following results: with controlled initial pH, Rhodotorula sp. produced maximum biomass (DO) and polygalacturonase (PG) after 20 h (DO, 3.86; PG, 0.24 U x mL(-1)) of growth, and this level was sustained until the end of the culture; Leuconostoc sp. LLn1 synthesized more cells and polygalacturonase between 4 h (DO, 1.80; PG, 0.17 U x mL(-1)) and 24 h (DO, 3.90; PG, 0.27 U x mL(-1)) of culture. With uncontrolled initial pH, the cultures produced maximum biomass and polygalacturonase after 20 h (DO, 3.30; PG, 0.26 U x mL(-1)) for Rhodotorula sp. ONRh9 and 10 h (DO, 2.84; PG, 0.17 U x mL(-1)) for Leuconostoc sp. LLn1.

International audience; Twenty-five strains of actinomycetes were isolated from samples of water, soil and tree barks collected at two sites located in the northeast of Algeria. Antimicrobial activity was tested using the agar cylinder method against three Gram-positive bacteria, three Gram-negative bacteria, three yeasts and three filamentous fungi. Among the 25 isolates 14 (56%) strains showed an activity against at least one of the test-bacteria studied and two (8%) showed antifungal activity. Ninety-three percent of the active strains were identified by the universal PCR as belonging to the Streptomyces genus and 7% to the Actinomadura genus.