Time filter

Source Type

Gesheva V.,Bulgarian Academy of Science | Negoita T.,Romanian Polar Research Institute
Polar Biology | Year: 2012

Diversity of microorganisms plays an important role in the functioning of ecosystems and their response to large-scale environmental changes. Microbial soil communities from virgin Haswell Island, Antarctica, were studied using the serial dilution-spread plate method at two different temperatures. Microorganisms were identified by sporulation, morphological, chemotaxonomic assessment. Nitrogen-fixing cyanobacteria and microalgae prevailed in the samples. Representatives of Chamaesiphon, Dermocarpa, Fischerella, Oscillatoria, Prochlrococcus, Synechococcus, Chlorophyta were detected. Fungal assemblages comprised Aspergillus nidulans, Cladosporium cladosporioides, Alternaria alternata, Mortierella ramanniana, Penicillium verrucosum, Scopulariopsis fusca, Cladophialophora minutissima, Chaetomium gracile, Phoma herbarum,Phialophora fastigiata,Ulocladium consortiale and Candida sp. Actinomycetes were identified by morphological and chemotaxonomic assessment of cell-wall aminoacids and sugars as Streptomyces, Nocardia and Geodermatophilus. Some of the isolated microorganisms formed extracellular enzymes, others biosynthesized substances with antifungal and antibacterial activities. Single psychrotrophic strains have an ability to grow on n-paraffins and naphthalene, and thin-layer chromatographic analyses showed that they synthesized glycolipids. Assays for sugar moiety revealed that they contained different pentoses such as arabinose, xylose or deoxyhexose as rhamnose. © 2011 Springer-Verlag.

Bahrim G.,University of Galati | Butu N.,KUK | Negoita T.G.,Romanian Polar Research Institute
Romanian Biotechnological Letters | Year: 2010

Several biotechnological aspects regarding the increase in transglutaminase biosynthesis yield were studied. The Streptomyces sp. strains used in this study, coded MIUG 6P, MIUG 7P and MIUG 13P, were isolated from soils from the East Antarctic coast. These had the best results in terms of transglutaminase synthesis, thus confirming the results of a previous study concerning the isolation and strains selection of good transglutaminase producers. Amongst these, strain coded MIUG 13P had the ability to produce 0.20 UA of transglutaminase per mL of crude extract, and was thus chosen to identify the optimal composition for the fermentative medium using Response surface methodology (RSM). Response surface methodology was further used to determine the optimum values of the process variables for enzyme production. The fit of the quadratic model was found to be significant. After submerged cultivation on the optimized fermentative medium, the enzymatic activity of the Streptomyces strain MIUG 13P showed a significant increase. © 2010 University of Bucharest.

Cotarlet M.,University of Galati | Bahrim G.,University of Galati | Negoita T.,Romanian Polar Research Institute | Stougaard P.,Copenhagen University
Romanian Biotechnological Letters | Year: 2010

The efficiency of different methods for chromosomal DNA extraction from polar streptomycetes strains was studied. The extraction yield and the purity of the chromosomal DNA were correlated with the microoganism type and method, respectively with the kits used. By using the microwave method or FastDNA® Kit (Qbiogene, Inc., CA) DNA yields were not sufficient for performing further PCR experiments. The explanation can lead that the streptomycetes are polar bacteria adapted at lower temperatures, with a hard cell membrane, difficult to cleave, or these filamentous bacteria had develop surviving strategies to protect themselves at low temperatures. High yields of the pure DNA were obtained using PowerSoil™ DNA Isolation Kit Sample (MO BIO Laboratories Inc.), a lot for the next steps of purification and sequencing. © 2010 University of Bucharest.

Cotarlet M.,University of Galati | Bahrim G.E.,University of Galati | Negoita T.G.,Romanian Polar Research Institute | Stougaard P.,Copenhagen University
Notulae Botanicae Horti Agrobotanici Cluj-Napoca | Year: 2010

Novel polar streptomycetes coded 4 Alga, P2C4 and MIUG 12P, isolated from soil and vegetation samples prelevated from East Antarctica, were genetically and biochemically characterized in order to set up the phylogeny and to identify their capability to grow at lower temperature and to generate cold-active amylase and protease. The 16S rRNA gene sequence of isolate coded 4 Alga was 100% identical to sequences of Streptomyces sp. isolates from Norway and from the Solomon Islands, which also were the closest relatives of P2C4 (99.53%) and MIUG 12P (99.53%) isolates. The data emphasised the skills of the strains Streptomyces 4 Alga, Streptomyces P2C4 and Streptomyces MIUG 12P to biosynthesize cold-adapted amylases and proteases suitable in bioconversion processes at low temperature. These results are quite valuable, because only few streptomycetes, particularly the psychrotolerant ones, have so far been explored for their enzymatic potential in cold conditions.

Cotarlet M.,Romanian Polar Research Institute | Negoita T.G.H.,Romanian Polar Research Institute | Bahrim G.E.,University of Jos | Stougaard P.,Copenhagen University
Brazilian Journal of Microbiology | Year: 2011

The aim of this study was to isolate novel enzyme-producing bacteria from vegetation samples from East Antarctica and also to characterize them genetically and biochemically in order to establish their phylogeny. The ability to grow at low temperature and to produce amylases and proteases cold-active was also tested. The results of the 16S rRNA gene sequence analysis showed that the 4 Alga rRNA was 100% identical to the sequences of Streptomyces sp. rRNA from Norway and from the Solomon Islands. The Streptomyces grew well in submerged system at 20°C, cells multiplication up to stationary phase being drastically increased after 120 h of submerged cultivation. The beta-amylase production reached a maximum peak after seven days, while alpha-amylase and proteases were performing biosynthesis after nine days of submerged cultivation at 20°C. Newly Streptomyces were able to produce amylase and proteases in a cold environment. The ability to adapt to low temperature of these enzymes could make them valuable ingredients for detergents, the food industry and bioremediation processes which require low temperatures.

Discover hidden collaborations