The taxonomic position of an aerobic actinobacterial strain, BMG841(T), isolated from the Bulla R... more The taxonomic position of an aerobic actinobacterial strain, BMG841(T), isolated from the Bulla Regia monument (Tunisia) and exhibiting a high resistance to gamma-radiation (D10 ~9 kGy) was determined using polyphasic approach. The optimal growth range was found to be 25-35 °C at pH of 7.0-8.5. The strain was observed to form black dry colonies. Chemotaxonomic characteristics of the isolate showed a cell wall type III, with galactose and glucose as diagnostic sugars; phosphatidylcholine, phosphatidylinositol, diphosphatidylglycerol, phosphatidylethanolamine and an unidentified glycolipid as main polar lipids; and MK-9(H4) as the predominant menaquinone. The major cellular fatty acids were identified as iso-C16:0 and iso-C15:0. Phylogenetic analysis indicated that strain BMG841(T) represents a novel member of the genus Geodermatophilus with high 16S rRNA gene sequence identity with Geodermatophilus saharensis (98.28 %). Based on phylogenetic and phenotypic analysis, strain BMG841(T) ...
The Geodermatophilaceae are unique model systems to study the ability to thrive on or within ston... more The Geodermatophilaceae are unique model systems to study the ability to thrive on or within stones and their proteogenomes (referring to the whole protein arsenal encoded by the genome) could provide important insight into their adaptation mechanisms. Here we report the detailed comparative genome analysis of Blastococcus saxobsidens (Bs), Modestobacter marinus (Mm) and Geodermatophilus obscurus (Go) isolated respectively from the interior and the surface of calcarenite stones and from desert sandy soils. The genome-scale analysis of Bs, Mm and Go illustrates how adaptation to these niches can be achieved through various strategies including 'molecular tinkering/opportunism' as shown by the high proportion of lost, duplicated or horizontally transferred genes and ORFans. Using high-throughput discovery proteomics, the three proteomes under unstressed conditions were analyzed, highlighting the most abundant biomarkers and the main protein factors. Proteomic data corroborated previously demonstrated stone-related ecological distribution. For instance, these data showed starvation-inducible, biofilm-related and DNA-protection proteins as signatures of the microbes associated with the interior, surface and outside of stones, respectively.The ISME Journal advance online publication, 30 June 2015; doi:10.1038/ismej.2015.108.
ABSTRACT This work aims to evaluate the antibacterial activity of lyophilized aqueous extract of ... more ABSTRACT This work aims to evaluate the antibacterial activity of lyophilized aqueous extract of Coriaria myrtifolia against twenty three bacterial strains belonging to twelve main genera, known to be involved in some pathologies and / or in the food spoilage process: Bacillus sp., E. coli, E. hafnia, Enterococcus sp., Klebsiella sp,. Listeria monocytogenes, Pseudomonas sp., Salmonella sp., Serratia sp., Shigella sp., S. aureus and Streptomyces sp. To achieve this goal, the disk diffusion method was used. The study revealed that C. myrtifolia’s aqueous extract is active against most of the tested strains and that activity is proportional to its concentration. The intensity of inhibition depends on the extract’s concentration on one hand and on the bacterial species tested on the other hand. Indexing terms/Keywords: Coriaria myrtifolia, Aqueous extracts, Antibacterial activity.
An orange-black, Gram-positive, aerobic and gamma-ray resistant actinobacterium was isolated from... more An orange-black, Gram-positive, aerobic and gamma-ray resistant actinobacterium was isolated from the ruins of a Roman aqueduct located in Northern Tunisia. The optimal growth for the strain was found to be at 25-35 °C and at pH 6.0-9.5. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The peptidoglycan was found to contain meso-diaminopimelic acid as diagnostic diaminoacid. The main polar lipids were identified as phosphatidylcholine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, an unidentified glycolipid and an unidentified aminophospholipid; MK-9(H4) was found to be the dominant menaquinone and galactose was detected as the diagnostic sugar, with glucose, ribose and mannose also present. The major cellular fatty acids were identified as branched-chain saturated acids iso-C16:0, iso-C15:0 and iso-H-C16:0. The 16S rRNA gene showed 95.4-99.6 % sequence identity with the type stra...
The repeated failures reported in cultivating some microbial lineages are a major challenge in mi... more The repeated failures reported in cultivating some microbial lineages are a major challenge in microbial ecology and probably linked, in the case of Frankia microsymbionts to atypical patterns of auxotrophy. Comparative genomics of the so far uncultured cluster-2 Candidatus Frankia datiscae Dg1, with cultivated Frankiae has revealed genome reduction, but no obvious physiological impairments. A direct physiological assay on nodule tissues from Coriaria myrtifolia infected with a closely-related strain permitted the identification of a requirement for alkaline conditions. A high pH growth medium permitted the recovery of a slow-growing actinobacterium. The strain obtained, called BMG5.1, has short hyphae, produced diazovesicles in nitrogen-free media, and fulfilled Koch's postulates by inducing effective nodules on axenically grown Coriaria spp. and Datisca glomerata. Analysis of the draft genome confirmed its close proximity to the Candidatus Frankia datiscae Dg1 genome with the ...
A total of 66 fluorescent pseudomonads strains isolated from diverse Tunisian environmental bioty... more A total of 66 fluorescent pseudomonads strains isolated from diverse Tunisian environmental biotypes (wastewater, compost, wastewater treatment plant, etc.) were analysed by two polymerase chain reaction (PCR)-based methods, 16S-23S intergenic spacer regions (ITS)-PCR and repetitive extragenic palindromic (BOX)-PCR. These typing techniques were evaluated to assess their usefulness as tool to study the Pseudomonas diversity within this complex group. Genetic analysis using ITS-and BOX-PCR generated respectively 12 and 45 distinct profiles. Phylogenetic relationships within fluorescent pseudomonads were examined by analyzing partial 16S rRNA and rpoB genes sequences. The phylogenetic resolution of the rpoB tree was higher than that of the 16S rRNA tree. Moreover, the sequencing of the rpoB gene has recognized 13 different species and sub-species, while the 16 rRNA gene sequencing differentiated only 9 species. Key words: Fluorescent pseudomonads, 16S-23S intergenic spacer regions (ITS...
International Journal of Systematic and Evolutionary Microbiology, 2015
A novel gamma-radiation-resistant and Gram positive actinobacterium designated BMG8133T was isola... more A novel gamma-radiation-resistant and Gram positive actinobacterium designated BMG8133T was isolated from a limestone collected in the Sahara desert of Tunisia. The strain produced dry pale pink colonies with an optimum growth at 35-40°C and pH 6.5-8.0. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The peptidoglycan contained meso-diaminopimelic acid as diagnostic diaminoacid. The main polar lipids were phosphatidylcholine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine and one unspecified glycolipid. MK-9(H4) was the dominant menaquinone. Galactose and glucose was detected as diagnostic sugar. The major cellular fatty acids were branched-chain saturated acids iso-C16:0 and iso-C15:0. The DNA G+C content of the new strain is 74.5 %. The 16S rRNA gene sequence showed 98.3 % as highest sequence identity with Geodermatophilus ruber species. Based on phenotypic results and 16S rRNA gene sequence analysis, strain BMG8133T is proposed to represent a novel species, Geodermatophilus sabuli. Type strain is BMG8133T (=DSM 46844T = CECT 8820T).
Both eutrophication and thermal stratification lead to degradation of wastewater treatment effici... more Both eutrophication and thermal stratification lead to degradation of wastewater treatment efficiency and have a major effect on the wastewater pond biology, but their effects on phototrophic anoxygenic bacterial community is not as well understood. Terminal restriction fragment length polymorphism analysis proved to be a valuable technique that could resolve the diversity and shift of the purple anoxygenic phototrophic community composition in three stage wastewater stabilization ponds (WSP) exhibiting periodically red water phenomenon. Chemical and biological parameters confirmed the eutrophic state during the appearance of the red water. Concomitantly a decrease of ponds performances is reported with total removal percentage of 27, 36 and 43% for Total suspended solid (TSS), DBO5 and DCO, respectively. By targeting thepufM gene, 74 Terminal restriction fragments (TRFs) were detected in the three studied ponds which 78% were located in the anaerobic and facultative ponds. Simpson ...
In arid ecosystems environmental factors such as geoclimatic conditions and agricultural practice... more In arid ecosystems environmental factors such as geoclimatic conditions and agricultural practices are of major importance in shaping the diversity and functionality of plant-associated bacterial communities. Assessing the influence of such factors is a key to understand (i) the driving forces determining the shape of root-associated bacterial communities and (ii) the plant growth promoting (PGP) services they provide. Desert oasis environment was chosen as model ecosystem where agriculture is possible by the microclimate determined by the date palm cultivation. The bacterial communities in the soil fractions associated with the root system of date palms cultivated in seven oases in Tunisia were assessed by culture-independent and dependent approaches. According to 16S rRNA gene PCR-DGGE fingerprinting, the shapes of the date palm rhizosphere bacterial communities correlate with geoclimatic features along a north-south aridity transect. Despite the fact that the date palm root bacte...
The taxonomic position of an aerobic actinobacterial strain, BMG841(T), isolated from the Bulla R... more The taxonomic position of an aerobic actinobacterial strain, BMG841(T), isolated from the Bulla Regia monument (Tunisia) and exhibiting a high resistance to gamma-radiation (D10 ~9 kGy) was determined using polyphasic approach. The optimal growth range was found to be 25-35 °C at pH of 7.0-8.5. The strain was observed to form black dry colonies. Chemotaxonomic characteristics of the isolate showed a cell wall type III, with galactose and glucose as diagnostic sugars; phosphatidylcholine, phosphatidylinositol, diphosphatidylglycerol, phosphatidylethanolamine and an unidentified glycolipid as main polar lipids; and MK-9(H4) as the predominant menaquinone. The major cellular fatty acids were identified as iso-C16:0 and iso-C15:0. Phylogenetic analysis indicated that strain BMG841(T) represents a novel member of the genus Geodermatophilus with high 16S rRNA gene sequence identity with Geodermatophilus saharensis (98.28 %). Based on phylogenetic and phenotypic analysis, strain BMG841(T) ...
The Geodermatophilaceae are unique model systems to study the ability to thrive on or within ston... more The Geodermatophilaceae are unique model systems to study the ability to thrive on or within stones and their proteogenomes (referring to the whole protein arsenal encoded by the genome) could provide important insight into their adaptation mechanisms. Here we report the detailed comparative genome analysis of Blastococcus saxobsidens (Bs), Modestobacter marinus (Mm) and Geodermatophilus obscurus (Go) isolated respectively from the interior and the surface of calcarenite stones and from desert sandy soils. The genome-scale analysis of Bs, Mm and Go illustrates how adaptation to these niches can be achieved through various strategies including 'molecular tinkering/opportunism' as shown by the high proportion of lost, duplicated or horizontally transferred genes and ORFans. Using high-throughput discovery proteomics, the three proteomes under unstressed conditions were analyzed, highlighting the most abundant biomarkers and the main protein factors. Proteomic data corroborated previously demonstrated stone-related ecological distribution. For instance, these data showed starvation-inducible, biofilm-related and DNA-protection proteins as signatures of the microbes associated with the interior, surface and outside of stones, respectively.The ISME Journal advance online publication, 30 June 2015; doi:10.1038/ismej.2015.108.
ABSTRACT This work aims to evaluate the antibacterial activity of lyophilized aqueous extract of ... more ABSTRACT This work aims to evaluate the antibacterial activity of lyophilized aqueous extract of Coriaria myrtifolia against twenty three bacterial strains belonging to twelve main genera, known to be involved in some pathologies and / or in the food spoilage process: Bacillus sp., E. coli, E. hafnia, Enterococcus sp., Klebsiella sp,. Listeria monocytogenes, Pseudomonas sp., Salmonella sp., Serratia sp., Shigella sp., S. aureus and Streptomyces sp. To achieve this goal, the disk diffusion method was used. The study revealed that C. myrtifolia’s aqueous extract is active against most of the tested strains and that activity is proportional to its concentration. The intensity of inhibition depends on the extract’s concentration on one hand and on the bacterial species tested on the other hand. Indexing terms/Keywords: Coriaria myrtifolia, Aqueous extracts, Antibacterial activity.
An orange-black, Gram-positive, aerobic and gamma-ray resistant actinobacterium was isolated from... more An orange-black, Gram-positive, aerobic and gamma-ray resistant actinobacterium was isolated from the ruins of a Roman aqueduct located in Northern Tunisia. The optimal growth for the strain was found to be at 25-35 °C and at pH 6.0-9.5. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The peptidoglycan was found to contain meso-diaminopimelic acid as diagnostic diaminoacid. The main polar lipids were identified as phosphatidylcholine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, an unidentified glycolipid and an unidentified aminophospholipid; MK-9(H4) was found to be the dominant menaquinone and galactose was detected as the diagnostic sugar, with glucose, ribose and mannose also present. The major cellular fatty acids were identified as branched-chain saturated acids iso-C16:0, iso-C15:0 and iso-H-C16:0. The 16S rRNA gene showed 95.4-99.6 % sequence identity with the type stra...
The repeated failures reported in cultivating some microbial lineages are a major challenge in mi... more The repeated failures reported in cultivating some microbial lineages are a major challenge in microbial ecology and probably linked, in the case of Frankia microsymbionts to atypical patterns of auxotrophy. Comparative genomics of the so far uncultured cluster-2 Candidatus Frankia datiscae Dg1, with cultivated Frankiae has revealed genome reduction, but no obvious physiological impairments. A direct physiological assay on nodule tissues from Coriaria myrtifolia infected with a closely-related strain permitted the identification of a requirement for alkaline conditions. A high pH growth medium permitted the recovery of a slow-growing actinobacterium. The strain obtained, called BMG5.1, has short hyphae, produced diazovesicles in nitrogen-free media, and fulfilled Koch's postulates by inducing effective nodules on axenically grown Coriaria spp. and Datisca glomerata. Analysis of the draft genome confirmed its close proximity to the Candidatus Frankia datiscae Dg1 genome with the ...
A total of 66 fluorescent pseudomonads strains isolated from diverse Tunisian environmental bioty... more A total of 66 fluorescent pseudomonads strains isolated from diverse Tunisian environmental biotypes (wastewater, compost, wastewater treatment plant, etc.) were analysed by two polymerase chain reaction (PCR)-based methods, 16S-23S intergenic spacer regions (ITS)-PCR and repetitive extragenic palindromic (BOX)-PCR. These typing techniques were evaluated to assess their usefulness as tool to study the Pseudomonas diversity within this complex group. Genetic analysis using ITS-and BOX-PCR generated respectively 12 and 45 distinct profiles. Phylogenetic relationships within fluorescent pseudomonads were examined by analyzing partial 16S rRNA and rpoB genes sequences. The phylogenetic resolution of the rpoB tree was higher than that of the 16S rRNA tree. Moreover, the sequencing of the rpoB gene has recognized 13 different species and sub-species, while the 16 rRNA gene sequencing differentiated only 9 species. Key words: Fluorescent pseudomonads, 16S-23S intergenic spacer regions (ITS...
International Journal of Systematic and Evolutionary Microbiology, 2015
A novel gamma-radiation-resistant and Gram positive actinobacterium designated BMG8133T was isola... more A novel gamma-radiation-resistant and Gram positive actinobacterium designated BMG8133T was isolated from a limestone collected in the Sahara desert of Tunisia. The strain produced dry pale pink colonies with an optimum growth at 35-40°C and pH 6.5-8.0. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The peptidoglycan contained meso-diaminopimelic acid as diagnostic diaminoacid. The main polar lipids were phosphatidylcholine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine and one unspecified glycolipid. MK-9(H4) was the dominant menaquinone. Galactose and glucose was detected as diagnostic sugar. The major cellular fatty acids were branched-chain saturated acids iso-C16:0 and iso-C15:0. The DNA G+C content of the new strain is 74.5 %. The 16S rRNA gene sequence showed 98.3 % as highest sequence identity with Geodermatophilus ruber species. Based on phenotypic results and 16S rRNA gene sequence analysis, strain BMG8133T is proposed to represent a novel species, Geodermatophilus sabuli. Type strain is BMG8133T (=DSM 46844T = CECT 8820T).
Both eutrophication and thermal stratification lead to degradation of wastewater treatment effici... more Both eutrophication and thermal stratification lead to degradation of wastewater treatment efficiency and have a major effect on the wastewater pond biology, but their effects on phototrophic anoxygenic bacterial community is not as well understood. Terminal restriction fragment length polymorphism analysis proved to be a valuable technique that could resolve the diversity and shift of the purple anoxygenic phototrophic community composition in three stage wastewater stabilization ponds (WSP) exhibiting periodically red water phenomenon. Chemical and biological parameters confirmed the eutrophic state during the appearance of the red water. Concomitantly a decrease of ponds performances is reported with total removal percentage of 27, 36 and 43% for Total suspended solid (TSS), DBO5 and DCO, respectively. By targeting thepufM gene, 74 Terminal restriction fragments (TRFs) were detected in the three studied ponds which 78% were located in the anaerobic and facultative ponds. Simpson ...
In arid ecosystems environmental factors such as geoclimatic conditions and agricultural practice... more In arid ecosystems environmental factors such as geoclimatic conditions and agricultural practices are of major importance in shaping the diversity and functionality of plant-associated bacterial communities. Assessing the influence of such factors is a key to understand (i) the driving forces determining the shape of root-associated bacterial communities and (ii) the plant growth promoting (PGP) services they provide. Desert oasis environment was chosen as model ecosystem where agriculture is possible by the microclimate determined by the date palm cultivation. The bacterial communities in the soil fractions associated with the root system of date palms cultivated in seven oases in Tunisia were assessed by culture-independent and dependent approaches. According to 16S rRNA gene PCR-DGGE fingerprinting, the shapes of the date palm rhizosphere bacterial communities correlate with geoclimatic features along a north-south aridity transect. Despite the fact that the date palm root bacte...
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Papers by Maher Gtari