Diversity and biosynthetic potential of culturable aerobic heterotrophic bacteria isolated from Magura Cave, Bulgaria

Biocapacity of bacteria inhabiting karstic caves to produce valuable biologically active compounds is still slightly investigated. A total of 46 culturable heterotrophic bacteria were isolated under aerobic conditions from the Gallery with pre-historical drawings in Magura Cave, Bulgaria. Phylogenetic analysis revealed that most of bacterial isolates aff iliated with Proteobacteria (63%), followed by Actinobacteria (10.9%), Bacteroidetes (10.9%), and Firmicutes (6.5%). A strong domination of Gram-negative bacteria (total 81%) belonging to nine genera: Serratia, Pseudomonas, Enterobacter, Sphingobacterium, Stenotrophomonas, Commamonas, Acinetobacter, Obesumbacterium, and Myroides, was observed. Gram-positive isolates were represented by the genera Bacillus, Arthrobacter, and Micrococcus. One isolate showed a signif icant phylogenetic distance to the closest neighbor and could represent а novel species. Heterotrophic bacterial isolates from Magura Cave were investigated for hydrolytic enzymes production, antimicrobial and hemolytic activity. Predominance of producers of protease (87%), followed by xanthan lyase (64%), lipase (40%), β-glycosidase (40%), and phytase (21%) was observed. Over 75% of the isolates demonstrated antimicrobial and hemolytic activity. The results suggest that heterotrophic bacteria isolated from Magura Cave could be a valuable source of industrially relevant psychrotolerant enzymes and bioactive metabolites. This study is a f irst report on the taxonomic composition and biological activity of culturable bacteria inhabiting a cave in Bulgaria

Archaeal and bacterial diversity in two hot springs from geothermal regions in Bulgaria as demostrated by 16S rRNA and GH-57 genes

Archaeal and bacterial diversity in two Bulgarian hot springs, geographically separated with different tectonic origin and different temperature of water was investigated exploring two genes, 16S rRNA and GH-57. Archaeal diversity was significantly higher in the hotter spring Levunovo (LV) (82°C); on the contrary, bacterial diversity was higher in the spring Vetren Dol (VD) (68°C). The analyzed clones from LV library were referred to twenty eight different sequence types belonging to five archaeal groups from Crenarchaeota and Euryarchaeota. A domination of two groups was observed, Candidate Thaumarchaeota and Methanosarcinales. The majority of the clones from VD were referred to HWCG (Hot Water Crenarchaeotic Group). The formation of a group of thermophiles in the order Methanosarcinales was suggested. Phylogenetic analysis revealed high numbers of novel sequences, more than one third of archaeal and half of the bacterial phylotypes displayed similarity lower than 97% with known ones. The retrieved GH-57 gene sequences showed a complex phylogenic distribution. The main part of the retrieved homologous GH-57 sequences affiliated with bacterial phyla Bacteroidetes, Deltaproteobacteria, Candidate Saccharibacteria and affiliation of almost half of the analyzed sequences is not fully resolved. GH-57 gene analysis allows an increased resolution of the biodiversity assessment and in depth analysis of specific taxonomic groups. [Int Microbiol 18(4):217-223 (2015)]Keywords: Archaea · hot spring · phylogenetic analysis · 16S rRNA gene · GH-57 gen

Problems and solutions by the application of Julia set theory to one-dot and multi-dots numerical methods

In 1977 Hubbard developed the ideas of Cayley (1879) and solved in particular the Newton-Fourier imaginary problem. We solve the Newton-Fourier and the Chebyshev-Fourier imaginary problems completely. It is known that the application of Julia set theory is possible to the one-dot numerical method like the Newton's method for computing solution of the nonlinear equations. The secants method is the two-dots numerical method and the application of Julia set theory to it is not demonstrated. Previously we have defined two one-dot combinations: the Newton's-secants and the Chebyshev's-secants methods and have used the escape time algorithm to analyse the application of Julia set theory to these two combinations in some special cases. We consider and solve the Newton's-secants and Tchebicheff's-secants imaginary problems completely

The Players in Airport Ground Handling:a New Typology Reflecting the International Expansion

The paper deals with the global nature of some players in airport ground handling industry. We provide a comprehensive overview of factors that cause fragmentation in the ground handling industry to explain the context in which global players develop their business internationally. Using the modified versions of UNCTAD Geographical Spread Indices we investigate several ground handlers and design a new typology of ground handlers according to their international expansion: key global ground handlers, key interregional international ground, key international intraregional ground handlers and locally important handlers. Adding the dimension of product portfolio we create a two­dimensional grid enabling to analyse evolution of ground handling industry to reflect international expansion of key players in different ground handling services. Arguing via the organic growth and consolidation examples, we assume the shift of the industry towards multiproduct ground handling companies with extensive international presence in all world regions

Long-haul low-cost air services: revealing key competitive features of airline within airline strategy

In this paper, we reveal which elements of business models typical for low-cost carriers and full-service network carriers were used by Norwegian and AirAsia X to enter markets with long-haul services. Our findings show that the long-haul low-cost operation which was realized as "airline within airline" strategy can be sustainable if an efficient mix of elements belonging to both low-cost and traditional airline business models is implemented. According to our analysis, traditional airlines will cope with the competition of low-cost carriers on long-haul markets mainly in the segments of less price-sensitive leisure passengers and more price-sensitive business pas­sengers in the higher fare classes. Such long-haul low-cost innovation can also generate a new demand for long-haul services supplying the market with an unbundled product for passengers in a very price-sensitive segment

Explanatory Analysis of Ancillary Revenues: Case Study of Three European Airlines

This paper quantifies an impact of ancillary revenues on changes of airlines total revenues using the data of three European low-cost airlines during the period from 2006 to 2011. The analysis reveals that ancillary revenues are important in generating total revenues in a low cost airlines group in terms of dynamics and subsequent influence on profit/loss result. The research findings confirmed that ancillary revenues influenced changes of total revenues significantly achieving in prevailing cases double-digit percentage share in the changes of total revenues expressed as a whole. So, quantified impact of ancillary revenues dynamics on dynamic of total revenues is undoubtly important for overall dynamics of airlines total revenues. Our analysis based on quantitative approach of explanatory analysis also clearly identified ancillary revenues as pro-operational profit driver through its positive and not marginal impact on dynamics in total airlines revenues. This disclosure is in line with general assumption of considerable role of ancillary revenues in low cost airlines economics

Diversity and biosynthetic potential of culturable aerobic heterotrophic bacteria isolated from Magura Cave, Bulgaria

Biocapacity of bacteria inhabiting karstic caves to produce valuable biologically active compounds is still slightly investigated. A total of 46 culturable heterotrophic bacteria were isolated under aerobic conditions from the Gallery with pre-historical drawings in MaguraCave, Bulgaria. Phylogenetic analysis revealed that most of bacterial isolates affiliated with Proteobacteria (63%), followed by Actinobacteria (10.9%), Bacteroidetes (10.9%), and Firmicutes (6.5%). A strong domination of Gram-negative bacteria (total 81%) belonging to nine genera: Serratia, Pseudomonas, Enterobacter, Sphingobacterium, Stenotrophomonas, Commamonas, Acinetobacter, Obesumbacterium, and Myroides, was observed. Gram-positive isolates were represented by the genera Bacillus, Arthrobacter, and Micrococcus. One isolate showed a significant phylogenetic distance to the closest neighbor and could represent а novel species. Heterotrophic bacterial isolates from MaguraCave were investigated for hydrolytic enzymes production, antimicrobial and hemolytic activity. Predominance of producers of protease (87%), followed by xanthan lyase (64%), lipase (40%), β-glycosidase (40%), and phytase (21%) was observed. Over 75% of the isolates demonstrated antimicrobial and hemolytic activity. The results suggest that heterotrophic bacteria isolated from MaguraCave could be a valuable source of industrially relevant psychrotolerant enzymes and bioactive metabolites. This study is a first report on the taxonomic composition and biological activity of culturable bacteria inhabiting a cave in Bulgaria