Characterization of Erwinia amylovora strains from Bulgaria by pulsed-field gel electrophoresis

The aim of this study was to characterize genetically Bulgarian Erwinia amylovora strains using pulsed-field gel electrophoresis (PFGE) analysis. Fifty E. amylovora strains isolated from different hosts, locations, as well as in different years were analysed by PFGE after XbaI, SpeI, and XhoI digestion of the genomic DNA. The strains were distributed into four groups according to their XbaI-generated profile. About 82% of the strains displayed a PFGE profile identical to that of type Pt2. Three strains belonged to the Central Europe Pt1 type. Two new PFGE profiles, not reported so far, were established--one for a strain isolated from Malus domestica and another for all Fragaria spp. strains. The same grouping of the strains was obtained after analysis of the SpeI digestion patterns. On the basis of PFGE profiles, after XbaI and SpeI digestion, a genetic differentiation between the strains associated with subfamily Maloideae and subfamily Rosoideae was revealed. The presence of more than one PFGE profile in the population of E. amylovora in Bulgaria suggests a multiple source of inoculum.     

Biomass, protein- and carbohydrate-composition of phytoplankton in Varna Bay, Black Sea

It was shown that phytoplankton from the Varna Bay, Black Sea, has significantly more suspended carbohydrates, proteins and biomass in July than in April. The dominant species were Bacillariophyceae and Dinophyceae. Electrophoretic and fluorescent spectra have shown the main differences in molecular weight and stability of phytoplankton proteins. Phytoplankton included specific proteins distributed over a limited range of molecular weights between 14 and 72 kilodaltons (kDa). The most abundant protein constituents in phytoplankton samples collected in April were around 45–55 kDa. The seasonal variations of the environment influence the quantitative and qualitative changes in phytoplankton.     

Calcium ions and the differentiation of Streptomyces hygroscopicus 155, a producer of an antibiotic complex]

The effect of Ca2+ on differentiation of Streptomyces hygroscopicus 155 and its inactive variant 155-0 was studied. Addition of Ca2+ to the medium induced formation of the aerial mycelium in the inactive variant and accelerated formation of the aerial mycelium in the parent strain. The inhibitory effect of EGTA, verapamil, nifedipin, chlorpromazine and dilthiazeme on the aerial mycelium formation demonstrated the physiological role of Ca2+ in the process. Addition of pandavir (nigericin) and azalomycin B, the antibiotics produced by the streptomycete, induced formation of the aerial mycelium in the inactive variant. The effect was higher in the presence of Ca2+. Streptomyces hygroscopicus 155 and its inactive variant synthesized a proteolytic complex containing metalloproteases and trypsin-like proteases. The total proteolytic activity of the inactive variant was lower than that of the parent strain. Addition of Ca2+ to the medium stimulated their proteolytic activity. The inducing action of the antibiotics produced by the parent strain on differentiation of S.hygroscopicus 155-0 and the increase of their action in the presence of Ca2+ suggested that they controlled the differentiation and that such a function of the antibiotics expressed itself through the Ca2+ signal system.     

Cytogenetic characterization of the Trinidad endemic, Arachnocoris trinitatus Bergroth: the first data for the tribe Arachnocorini (Heteroptera: Cimicomorpha: Nabidae)

As an extension of the ongoing cytogenetic studies of the bug family Nabidae (Heteroptera: Cimicomorpha), the first evidence for the tribe Arachnocorini (the subfamily Nabinae), with reference to the Trinidad endemic, Arachnocoris trinitatus Bergroth, is provided. This is an attempt to gain a better insight into the evolution, systematics and within-family relationships of the family Nabidae. The studies were conducted using a number of cytogenetic techniques. The male karyotype (chromosome number and size; sex chromosome system; NOR location; C-heterochromatin amount, distribution and characterization in terms of the presence of AT-rich and GC-rich DNA), and male meiosis with particular emphasis on the behavior of the sex chromosomes in metaphase II are described. Also investigated are the male and female internal reproductive organs with special reference to the number of follicles in a testis and the number of ovarioles in an ovary. A. trinitatus was found to display a number of characters differentiating it from all hitherto studied nabid species placed in the tribe Nabini of the subfamily Nabinae, and in the tribe Prostemmatini of the subfamily Prostemmatinae. Among these characters are chromosome number 2n = 12 (10 + XY), the lowest within the family, nucleolus organizer regions (NORs) situated on the autosomes rather than on the sex chromosomes as is the case in other nabid species, and testes composed of 3 follicles but not of 7 as in other nabids. All the data obtained suggest many transformations during the evolution ofA. trinitatus.     

Effect of protoplasting on antibiotic activity and resistance in the strain Streptomyces hygroscopicus 155]

The influence of protoplasting and protoplast regeneration in the presence of polyethylene glycol on antibiotic activity, components of antibiotic complexes and antibiotic resistance in Streptomyces hygroscopicus 155 was studied. It was shown that the protoplasting and protoplast regeneration influenced the antibiotic activity. The protoplast fusion resulted in increased isolation of variants with higher antibiotic activity. The processes also affected the components of the antibiotic complexes but had no effect on the strain resistance to some antibiotics.     

New host plants of Erwinia amylovora in Bulgaria

Nine strains of Erwinia amylovora were isolated from new host plants in Bulgaria--chokeberry and strawberry. The strains were characterized morphologically and biochemically using the API 20E and BIOLOG system. It was established that they showed three different API 20E metabolic profiles, not found by previous studies of E. amylovora. All strains were identified as E. amylovora due to their metabolic fingerprint patterns obtained by the BIOLOG system. The identification was confirmed by PCR amplification of a specific region of plasmid pEA29 and genome ams-region. This study is the first characterization and identification of E. amylovora strains isolated from chokeberry and strawberry by the API 20E and BIOLOG system and by polymerase chain reaction.     

Physiological diversity of bacterial communities from different soil locations on Livingston Island, South Shetland archipelago, Antarctica

Terrestrial food webs of Antarctica are simple and dominated by microorganisms. Soil bacteria play an important role in nutrient cycling, yet little is known about their capacity to utilize different carbon sources and to participate in site nutrient turnover. Biolog EcoPlate? was applied to study the catabolic activity and physiological diversity of bacteria inhabiting the soil of moss, vascular plants, and fell field habitats from Livingston Island, Antarctica. Additionally, the number of oligotrophic and copiotrophic bacteria was counted by the agar plate method. Results indicated a lack of site-specific distribution of bacterial abundance, in contrast to bacterial catabolic activity and community level physiological profiles. Community level physiological profiles revealed a common capacity of soil bacteria to intensively utilize polyols, which are cryoprotectants widely produced by Antarctic organisms, as well as site-specific phenolic compounds (vegetated habitats), amino acids/amines (moss habitats), carbohydrates and carboxylic acids (fell field habitat). It was concluded that the physiology of soil bacteria is habitat specific concerning both the rate of catabolic activity and pattern of carbon source utilization.