Molecular identification of vaginal lactobacilli isolated from Bulgarian women

Lactobacilli play an important role in maintaining the vaginal health of women. The development of suitable bacterial replacement therapies for the treatment of vaginosis requires knowledge of the vaginal lactobacilli species representation. The aim of this study was to identify at the species level vaginal Lactobacillus isolates obtained from Bulgarian women in childbearing age by using different molecular methods. Twenty-two strains of lactobacilli isolated from vaginal samples were identified and grouped according to their genetic relatedness. A combined approach, which included amplified ribosomal DNA restriction analysis (ARDRA), ribotyping and polymerase chain reaction (PCR) with species-specific oligonucleotide primers was applied. All vaginal isolates were grouped into 5 clusters in␣comparison with a set of 21 reference strains based␣on the initial ARDRA results, which was then confirmed by ribotyping. Finally, the strains were subjected to PCR analysis with eight different species-specific primer pairs, which allowed most of␣them to be classified as belonging to one of␣the␣following species: Lactobacillus crispatus, Lactobacillus fermentum, Lactobacillus gasseri, Lactobacillus helveticus and Lactobacillus plantarum. In conclusion, this study suggests that the most straightforward identification strategy for vaginal lactobacilli would be grouping by ARDRA or ribotyping, followed by PCR specific primers identification at species level.     

Surface characteristics of lactobacilli isolated from human vagina

In the present paper, the taxonomic classification of 134 lactobacilli isolates from vaginal samples of 200 women of Tucumán, Argentina, is reported. They were clustered in three metabolic groups of the genus Lactobacillus, most belonging to the obligately homofermentative group (56%), mainly represented by Lactobacillus delbrueckii subsp. delbrueckii and L. acidophilus. In the facultatively heterofermentative group (24%), the dominant species were L. paracasei subsp. paracasei and L. agilis, and in the obligately heterofermentative group (20%), L. brevis was the dominant species. All strains were studied for surface characteristics and adhesion-predicting properties. A correlation between the methods employed for hydrophobicity testing of the different isolates (Microbial Adhesion to Hydrocarbons and Salt Aggregation Test) is reported. Most strains were highly hydrophobic. Their hemagglutination capability with human erythrocytes was also tested, which was positive only for a few strains. Some isolates were self-aggregating. From our results, strains that shared the properties assayed were selected for further testing of some other desirable characteristics, such as antagonistic substance production, adhesion to biological substrates, and appropriate technological properties, to suggest the elaboration of a probiotic for the vaginal tract.     

Toward an Alternative Therapeutic Approach for Skin Infections: Antagonistic Activity of Lactobacilli Against Antibiotic-Resistant Staphylococcus aureus and Pseudomonas aeruginosa

The wide spread of antimicrobial resistance has urged the need of alternative therapeutic approach. In this context, probiotic lactobacilli have been reported for the prevention and treatment of many gastrointestinal and urogenital infections. However, very little is known about their antagonistic activity against skin pathogens. Accordingly, the present study aimed to investigate the potential of lactobacilli to interfere with pathogenesis features of two antibiotic-resistant skin pathogens, namely methicillin-resistant Staphylococcus aureus and multiple-resistant Pseudomonas aeruginosa. A total of 49 lactobacilli were recovered, identified and tested for their antagonistic activities against the aforementioned pathogens. Of these, eight isolates were capable of blocking the adherence of pathogens to mammalian cells independent of the skin pathogen tested or model adopted. Moreover, three Lactobacillus isolates (LRA4, LC2 and LR5) effectively prevented the pathogen internalization into epithelial cells in addition to potentiating phagocyte-mediated pathogen killing. Interestingly, the lactobacilli LC2, LF9 and LRA4 markedly inhibited the growth of P. aeruginosa and S. aureus isolates in coculture experiments. Besides, the lactobacilli LRA4, LC2, LR5 and LF9 have counteracted pathogen cytotoxicity. Taken together, the present study revealed some inhibitory activities of lactobacilli against two antibiotic-resistant skin pathogens. Moreover, it revealed two lactobacilli, namely LC2 and LRA4, with antagonistic capacity against different virulence determinants of skin pathogens. These lactobacilli are considered promising probiotic candidates that may represent an alternative therapeutic approach for skin infections.     

Characterization of vaginal lactobacilli in women after kidney transplantation

Limited number of publications described vaginal microflora after kidney transplantation. Our PubMed search revealed only 18 publications including words “vaginal bacteria &; kidney transplant” in the period of 1978–2011. The aim of this study was to characterize lactobacilli isolated from vaginal swabs of women after kidney transplantation, compared with healthy women. Eighteen renal transplant recipients (mean age 36.1) and 20 healthy women (mean age 36.0) were evaluated. Lactobacilli were cultured on MRS and Columbia blood agars. Biochemical identification with API 50 CHL (bioMerieux, Marcy L’Etoile, France) and multiplex PCR according to Song et al. was performed. Lactobacilli were tested for production of H₂O₂. Minimal inhibitory concentrations (MICs) of selected antimicrobial agents were determined with E-tests (bioMerieux, Marcy L’Etoile, France) and interpreted with CLSI and EUCAST criteria. No bacterial vaginosis was found among studied women. Two strains of group I were identified as Lactobacillus delbrueckii; 18 strains as Lactobacillus gasseri and 15 strains as Lactobacillus crispatus. Only 3 strains from group II were not identified by species-specific mPCR. Group IV was represented with 2 unidentified strains. Vaginal lactobacilli isolated from healthy women represented more homogenous group compared with heterogenous renal transplant recipients. Biochemical identification of lactobacilli by API 50 CHL kits was concordant with mPCR results only in 7 cases (17.5%), all 7 strains were identified as L. crispatus. Majority (93%) of lactobacilli were H₂O₂ producers. All isolated lactobacilli (100%) demonstrated high resistance to metronidazole (MIC > 256 μg/ml). Only 2 strains resistant to vancomycin (MICs: 32 and 256 μg/ml respectively), in the study and control group, and one to moxifloxacin (MIC = 32 μg/ml), were found. Resistance to metronidazole and vancomycin was concordant in CLSI and EUCAST (2010) criteria. Although significant differences between lactobacilli isolated from vaginas of kidney transplant and healthy women were not demonstrated, we demonstrated strains resistant to metronidazole, vancomycin and moxifloxacin in groups of examined women. Our study was performed on a small group of kidney transplant recipients and further more detailed molecular studies on a larger group of patients are required to confirm our results.     

Adaptation and Probiotic Potential of Lactobacilli,Isolated from the Oral Cavity and Intestines of Healthy People

The present study shows that, from 300 Lactobacillus strains isolated from the oral cavity and large intestine of 600 healthy people, only 9 had high antagonistic activity against pathogens and opportunistic pathogens. All antagonistic strains of lactobacilli have been identified by 16S rRNA sequencing and assigned to four species: Lactobacillus fermentum, Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus casei. In addition, these lactobacilli appeared to be nonpathogenic and had some probiotic potential: the strains produced lactic acid and bacteriocins, showed high sensitivity to broad-spectrum antibiotics, and were capable of forming biofilms in vitro. With the help of PCR and specific primers, the presence of genes for prebacteriocins in L. plantarum (plnEF, plnJ, plnN) and L. rhamnosus (LGG_02380 and LGG_02400) has been revealed. It was found that intestinal strains of lactobacilli were resistant to hydrochloric acid and bile. Lactobacilli isolated from the oral cavity were characterized by a high degree of adhesion, whereas intestinal strains were characterized by average adhesion. Both types of lactobacilli had medium to high rates of auto-aggregation and hydrophobicity and could coaggregate with pathogens and opportunistic pathogens. Additionally, the ability of the lactobacilli strains to produce gasotransmitters, CH₄, CO₂, C₂H₆, CO, and NH₃, has been revealed.     

(GTG)<Subscript>5</Subscript>-PCR fingerprinting of lactobacilli isolated from cervix of healthy women

A group of lactobacilli isolated from the cervix of 31 healthy women was characterized by (GTG)₅-polymerase chain reaction (PCR) fingerprinting in order to evaluate this method for identification of vaginal lactobacilli. Obtained fingerprints were compared with profiles available in an in-house database of the CCM bacteria collection covering type and reference strains of multiple lactic acid bacteria including lactobacilli. Selected strains representing individual clusters were further identified by pheS gene sequencing. In total, six lactobacillus species were found among lactobacilli isolated from the cervix of healthy women. The (GTG)₅-PCR method identified Lactobacillus gasseri (11 strains), Lactobacillus fermentum (one), and some of the Lactobacillus jensenii strains (eight out of 11), but failed to identify the remaining strains, including the Lactobacillus crispatus (18), Lactobacillus mucosae (one), and Lactobacillus vaginalis (one) species. L. jensenii strains were distributed over two fingerprint clusters. The majority of samples was dominated by one (GTG)₅-PCR type. The rep-PCR fingerprinting using the (GTG)₅ primer allowed straightforward identification of many, but not all, isolates. This method has been shown to be a useful tool for fast screening and grouping of vaginal lactobacilli, but its combination with another identification method is needed to obtain reliable identification results. In addition, Lactobacillus acidophilus was not shown to be the most common inhabitant of the female genital tract as generally assumed.     

Virulence of Klebsiella pneumoniae Isolates Harboring bla KPC-2 Carbapenemase Gene in a Caenorhabditis elegans Model

Klebsiella pneumoniae carbapenemase (KPC) is a carbapenemase increasingly reported worldwide in Enterobacteriaceae. The aim of this study was to analyze the virulence of several KPC-2-producing K. pneumoniae isolates. The studied strains were (i) five KPC-2 clinical strains from different geographical origins, belonging to different ST-types and possessing plasmids of different incompatibility groups; (ii) seven transformants obtained after electroporation of either these natural KPC plasmids or a recombinant plasmid harboring only the bla _KPC-2 gene into reference strains K. pneumoniae ATCC10031/{"type":"entrez-protein","attrs":{"text":"CIP53153","term_id":"878514309","term_text":"CIP53153"}}CIP53153; and (iii) five clinical strains cured of plasmids. The virulence of K. pneumoniae isolates was evaluated in the Caenorhabditis elegans model. The clinical KPC producers and transformants were significantly less virulent (LT50: 5.5 days) than K. pneumoniae reference strain (LT50: 4.3 days) (p<0.01). However, the worldwide spread KPC-2 positive K. pneumoniae ST258 strains and reference strains containing plasmids extracted from K. pneumoniae ST258 strains had a higher virulence than KPC-2 strains belonging to other ST types (LT50: 5 days vs. 6 days, p<0.01). The increased virulence observed in cured strains confirmed this trend. The bla _KPC-2 gene itself was not associated to increased virulence.     

Improved Understanding of the Bacterial Vaginal Microbiota of Women before and after Probiotic Instillation

The vaginal bacterial microbiota of 19 premenopausal women was examined by PCR-denaturing gradient gel electrophoresis (DGGE) and sequencing of the V2-V3 region of the 16S rRNA gene. Ten of the women were studied further to investigate the effect and persistence of vaginally inserted capsules containing viable lactobacilli. PCR-DGGE indicated that most subjects had a microbiota represented by one to three dominant DNA fragments. Analysis of these fragments revealed that 79% of the women possessed sequences with high levels of similarity to Lactobacillus species sequences. Sequences homologous to Lactobacillus iners sequences were the most common and were detected in 42% of the women tested. Alteration of the vaginal microbiota could be detected by PCR-DGGE in several women after the instillation of lactobacilli. Additionally, randomly amplified polymorphic DNA analysis of lactobacilli isolated from selective media demonstrated that the exogenous strains could be detected for up to 21 days in some subjects. This study demonstrates that non-culture-based techniques, such as PCR-DGGE, are useful adjuncts for studies of the vaginal microbiota.     

Isolation of probiotic lactobacilli strains harboring l-asparaginase and arginine deiminase genes from human infant feces for their potential application in cancer prevention

The aim of this work was to isolate novel lactobacilli probiotic strains from human feces and screen them for the presence of two valuable antitumor genes—the arginine deiminase-encoding gene arcA and l-asparaginase-encoding gene ansA—for future potential therapeutic application in cancer prevention. Feces samples were collected from Egyptian infants. Forty-two isolates were determined as Lactobacillus sp. and selected for further characterization. Only 20 isolates exhibited good tolerance to pH 1.5, 0.3 % bile salts and moderate tolerance to pancreatic enzymes in addition to antagonistic action. These isolates were screened by PCR for the presence of the arcA and ansA genes. Three strains were selected and identified to subspecies levels by amplification and sequencing of 16S rRNA genes as Lactobacillus gasseri NM112 containing the ansA gene; Lactobacillus fermentum NM212; and Lactobacillus casei NM312 containing the arcA gene, and confirmed by determining enzyme activity. We conclude that these three strains can be suggested as probiotics with potential therapeutic effect against cancer.     

Effect of Two Probiotic Strains of Lactobacillus on In Vitro Adherence of Listeria monocytogenes,Streptococcus agalactiae,and Staphylococcus aureus to Vaginal Epithelial Cells

The lactobacilli probiotics maintain a normal vaginal biota and prevent disease recurrence. This microorganisms form a pellicle on the vaginal epithelium that acts as a biologic barrier against colonization by pathogenic bacteria. In this paper were realized assays of exclusion, competition, and displacement. For these test, vaginal epithelial cells, two strains of lactobacilli and pathogenic bacteria (Staphylococcus aureus, Streptococcus agalactiae and Listeria monocytogenes) were used. The lactobacilli strains showed a great capacity of adherence, with a mean of 83.5 ± 26.67 Lactobacillus fermentum cells and 56.2 ± 20.87 Lactobacillus rhamnosus cells per vaginal epithelial cells. L. fermentum and L. rhamnosus were able to reduce the adherence of S. aureus, S. agalactiae and L. monocytogenes in a significant level in this assay (P < 0.01). The lactobacilli used in this study protect the vaginal epithelium through a series of barriers and interference mechanisms. The aim of present study was to assess the ability of vaginal Lactobacillus strains, selected for their probiotic properties, to block the adherence of pathogenic microorganisms in vitro by displacement, competition, and exclusion mechanisms.     

Vaginal lactic acid bacteria in the mare: evaluation of the probiotic potential of native Lactobacillus spp. and Enterococcus spp. strains

Lactic acid bacteria (LAB) are important members of the human vaginal microbiota and their presence is considered beneficial. However, little is known about native vaginal bacteria in other animal species such as the horse. The aim of this work was to quantify the vaginal lactic acid bacteria and lactobacilli of mares and to establish if selected equine vaginal lactic acid bacteria, particularly Lactobacillus and Enterococcus spp. strains, could exhibit potential as probiotics. The vaginal lactic acid bacteria and lactobacilli of 26 mares were quantified by plate counts. Five strains (three Lactobacillus spp. and two Enterococcus spp.) were characterised and adhesion to vaginal epithelial cells, antimicrobial activity and ability to form biofilms were evaluated. Lactic acid bacteria were recovered from the 26 samples and lactobacilli counts were detected in 18 out of 26 mares (69%). Probiotic properties tested in this study varied among the isolates and showed promising features for their use as equine probiotics.     

Relationships between the probiotic and host indigenous lactobacilli under the conditions of mixed cultivation in vitro

Relationships between 5 Lactobacillus manufacturing strains, 458 cultures of indigenous lactobacilli isolated from the human digestive and vaginal tracts and 98 isolates from the feces of white rats and mice were under study. The study demonstrated that under the conditions of mixed in vitro cultivation of paired cultures, probiotic strains inhibited more than 60% of the indigenous lactobacilli isolates. L. acidophilus strain K3 III 24 had the widest spectrum of antagonistic activity. Antagonistic relationships between indigenous lactobacilli depended on the origin, individual features and the anatomical sites of the culture isolation. Based on these results it has to be suggested that probiotic lactobacilli are capable of inducing disbalance in the host indigenous lactoflora. While choosing probiotics the character of relationships between probiotic microorganisms and the indigenous lactobacilli of the future recipient is recommended to be preliminarily tested in vitro.     

Isolation and identification of new lactobacilli from goatling stomach and investigation of reuterin production in Lactobacillus reuteri strains

Five new strains of lactobacilli isolated from goatling??s stomach were identified by molecular?Cbiological approaches. Profiles of fermentable saccharides, Gram staining, and cell morphology were also determined. They were identified as Lactobacillus reuteri (strains KO4b, KO4m, KO5) and as Lactobacillus plantarum (strains KG1z, KG4). In DNA samples of all newly isolated L. reuteri strains as well as in L. reuteri E (Lreu E; originated from lamb), the part of gldC gene, coding large subunit of glycerol dehydratase, that is necessary for 3-hydroxypropionaldehyde (3-HPA; reuterin) production, was amplified using two designed primer sets. However, the 3-HPA production was revealed only in the strain Lreu E. It produced five- or ten-fold lower amount of 3-HPA in comparison with probiotic L. reuteri ATCC 55730 in aerobic or anaerobic conditions, respectively. Moreover, Lreu E completely lost its production ability after ca. five passages in MRS medium. The co-incubation of Lreu E, but not other L. reuteri isolates, with Escherichia coli re-induced 3-HPA production. In the case of L. reuteri ATCC 55730, the 3-HPA production increased more than four times after co-incubation with E. coli.     

Riboprinting and 16S rRNA Gene Sequencing for Identification of Brewery Pediococcus Isolates

A total of 46 brewery and 15 ATCC Pediococcus isolates were ribotyped using a Qualicon RiboPrinter. Of these, 41 isolates were identified as Pediococcus damnosus using EcoRI digestion. Three ATCC reference strains had patterns similar to each other and matched 17 of the brewery isolates. Six other brewing isolates were similar to ATCC 25249. The other 18 P. damnosus brewery isolates had unique patterns. Of the remaining brewing isolates, one was identified as P. parvulus, two were identified as P. acidilactici, and two were identified as unique Pediococcus species. The use of alternate restriction endonucleases indicated that PstI and PvuII could further differentiate some strains having identical EcoRI profiles. An acid-resistant P. damnosus isolate could be distinguished from non-acid-resistant varieties of the same species using PstI instead of EcoRI. 16S rRNA gene sequence analysis was compared to riboprinting for identifying pediococci. The complete 16S rRNA gene was PCR amplified and sequenced from seven brewery isolates and three ATCC references with distinctive riboprint patterns. The 16S rRNA gene sequences from six different brewery P. damnosus isolates were homologous with a high degree of similarity to the GenBank reference strain but were identical to each other and one ATCC strain with the exception of 1 bp in one strain. A slime-producing, beer spoilage isolate had 16S rRNA gene sequence homology to the P. acidilactici reference strain, in agreement with the riboprint data. Although 16S rRNA gene sequencing correctly identified the genus and species of the test Pediococcus isolates, riboprinting proved to be a better method for subspecies differentiation.     

Influence of carbohydrates on cell properties of <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis>

Lactobacilli represent normal commensals of the human body, particularly in the gut and vagina where they protect these environments from incoming pathogens via a variety of mechanisms. The influence of the carbohydrate source present in reconstituted MRS growth medium on the different cell properties of two Lactobacillus rhamnosus strains were examined. Two human vaginal isolates, BGHV719 and exopolysaccharide producer strain BGHV954 were analyzed. The results demonstrated that unlike in reconstituted MRS with glucose as a carbon source, the presence of fructose, mannose, or rhamnose, significantly reduced cell surface hydrophobicity of both strains. In addition, differences in cell wall protein composition of L. rhamnosus BGHV719 and alterations in colony mucoidity of L. rhamnosus BGHV954 were also demonstrated. Light and SEM microscopy revealed differences on the cellular level when BGHV719 was cultivated in the presence of different sugars. The results of this study point out the importance of complex relationships between growth medium composition and the different aspects of bacterial behavior, and call for more detailed analyses of versatile bacterial responses to the changes in the environment, including vaginal ecosystem. This is especially important since lactobacilli are amongst the most widely used of probiotics.     

Bacteriocin production and gene sequencing analysis from vaginal Lactobacillus strains

The human vagina is a complex and dynamic ecosystem containing an abundance of microorganisms. In women of childbearing age, this system is dominated by Lactobacillus spp. In the present work, seventeen newly isolated vaginal strains were identified by 16S rDNA sequencing and were investigated for their antimicrobial properties. Twelve of the isolated Lactobacillus strains showed activity against one or more microorganisms. Six and five of them produced substances that inhibited the growth of two different Klebsiella strains and Staphylococcus aureus, respectively. Two lactobacilli strains were active against an Escherichia coli strain, one isolate was active against an Enterococus faecalis strain and another lactobacilli strain showed antimicrobial activity against a Candida parapsilosis strain. The nature of the active compounds was additionally studied, and the presence of bacteriocin-like substances was proved. The genes related to the bacteriocin production in three of the newly isolated strains were identified and sequenced. The presence of gassericin A operon in the genome of the species Lactobacillus crispatus was described for the first time. The presence of antimicrobial activity contributes to their possible use as potential probiotic strains after further research.     

Vaginal versus Obstetric Infection Escherichia coli Isolates among Pregnant Women: Antimicrobial Resistance and Genetic Virulence Profile

Vaginal Escherichia coli colonization is related to obstetric infections and the consequent development of infections in newborns. Ampicillin resistance among E. coli strains is increasing, which is the main choice for treating empirically many obstetric and neonatal infections. Vaginal E. coli strains are very similar to extraintestinal pathogenic E. coli with regards to the virulence factors and the belonging to phylogroup B2. We studied the antimicrobial resistance and the genetic virulence profile of 82 E. coli isolates from 638 vaginal samples and 63 isolated from endometrial aspirate, placental and amniotic fluid samples from pregnant women with obstetric infections. The prevalence of E. coli in the vaginal samples was 13%, which was significant among women with associated risk factors during pregnancy, especially premature preterm rupture of membranes (p<0.0001). Sixty-five percent of the strains were ampicillin-resistant. The E. coli isolates causing obstetric infections showed higher resistance levels than vaginal isolates, particularly for gentamicin (p = 0.001). The most prevalent virulence factor genes were those related to the iron uptake systems revealing clear targets for interventions. More than 50% of the isolates belonged to the virulent B2 group possessing the highest number of virulence factor genes. The ampicillin-resistant isolates had high number of virulence factors primarily related to pathogenicity islands, and the remarkable gentamicin resistance in E. coli isolates from women presenting obstetric infections, the choice of the most appropriate empiric treatment and clinical management of pregnant women and neonates should be carefully made. Taking into account host-susceptibility, the heterogeneity of E. coli due to evolution over time and the geographical area, characterization of E. coli isolates colonizing the vagina and causing obstetric infections in different regions may help to develop interventions and avoid the aetiological link between maternal carriage and obstetric and subsequent puerperal infections.     

Screening for potential probiotic from spontaneously fermented non-dairy foods based on in vitro probiotic and safety properties

The aim of this study was to screen potential probiotic lactic acid bacteria from Chinese spontaneously fermented non-dairy foods by evaluating their probiotic and safety properties. All lactic acid bacteria (LAB) strains were identified by 16S rRNA gene sequencing. The in vitro probiotic tests included survival under low pH and bile salts, cell surface hydrophobicity, auto-aggregation, co-aggregation, antibacterial activity, and adherence ability to cells. The safety properties were evaluated based on hemolytic activity and antibiotic resistance profile. The salt tolerance, growth in litmus milk, and acidification ability were examined on selected potential probiotic LAB strains to investigate their potential use in food fermentation. A total of 122 strains were isolated and identified at the species level by 16S rRNA gene sequencing and included 62 Lactobacillus plantarum, 40 Weissella cibaria, 12 Lactobacillus brevis, 6 Weissella confusa, and 2 Lactobacillus sakei strains. One W. cibaria and nine L. plantarum isolates were selected based on their tolerance to low pH and bile salts. The hydrophobicity, auto-aggregation, co-aggregation, and antagonistic activities of these isolates varied greatly. All of the 10 selected strains showed multiple antibiotic resistance phenotypes and no hemolytic activity. The highest adhesion capacity to SW480 cells was observed with L. plantarum SK1. The isolates L. plantarum SK1, CB9, and CB10 were the most similar strains to Lactobacillus rhamnosus GG and selected for their high salt tolerance and acidifying activity. The results revealed strain-specific probiotic properties were and potential probiotics that can be used in the food industry.     

Assessing the diversity of bacterial communities from marine sponges and their bioactive compounds

Symbiotic bacteria play vital roles in the survival and health of marine sponges. Sponges harbor rich, diverse and species-specific microbial communities. Symbiotic marine bacteria have increasingly been reported as promising source of bioactive compounds. A culturomics-based study was undertaken to study the diversity of bacteria from marine sponges and their antimicrobial potential. We have collected three sponge samples i.e. Acanthaster carteri, Rhytisma fulvum (soft coral) and Haliclona caerulea from north region (Obhur) of Red Sea, Jeddah Saudi Arabia. Total of 144 bacterial strains were isolated from three marine sponges using culture dependent method. Screening of isolated strains showed only 37 (26%) isolates as antagonists against oomycetes pathogens (P. ultimum and P. capsici). Among 37 antagonistic bacteria, only 19 bacterial strains exhibited antibacterial activity against human pathogens (Methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 8739, Enterococcus faecalis ATCC 29212). Four major classes of bacteria i.e γ-Proteobacteria, α-Proteobacteria, Firmicutes and Actinobacteria were recorded from three marine sponges where γ-Proteobacteria was dominant class. One potential bacterial strain Halomonas sp. EA423 was selected for identification of bioactive metabolites using GC and LC-MS analyses. Bioactive compounds Sulfamerazine, Metronidazole-OH and Ibuprofen are detected from culture extract of strain Halomonas sp. EA423. Overall, this study gives insight into composition and diversity of antagonistic bacterial community of marine sponges and coral from Red Sea and presence of active metabolites from potential strain. Our results showed that these diverse and potential bacterial communities further need to be studied to exploit their biotechnological significance.     

Characterization of field isolates of Trichoderma antagonistic against Rhizoctonia solani

The aim of the present study was to characterize sixteen isolates of Trichoderma originating from a field of sugar beet where disease patches caused by Rhizoctonia solani were observed. Use of both molecular and morphological characteristics gave consistent identification of the isolates. Production of water-soluble and volatile inhibitors, mycoparasitism and induced systemic resistance in plant host were investigated using in vitro and in vivo tests in both sterilized and natural soils. This functional approach revealed the intra-specific diversity as well as biocontrol potential of the different isolates. Different antagonistic mechanisms were evident for different strains. The most antagonistic strain, T30 was identified as Trichoderma gamsii. This is the first report of an efficient antagonistic strain of T. gamsii being able to reduce the disease in different conditions. The ability to produce water-soluble inhibitors or coil around the hyphae of the pathogen in vitro was not related to the disease reduction in vivo. Additionally, the strains collected from the high disease areas in the field were better antagonists. The antagonistic activity was not characteristic of a species but that of a population.