Judit Makk

Algological and bacteriological investigations on reed periphyton in Lake Velencei, Hungary

In the shallow Lake Velencei (surface area 24.5 km2) reed communities (Scirpo-Phragmitetum) are of great significance due to extensive metabolic activity of algal-bacterial associations developing on their submerged surfaces. Samples for algological and bacteriological studies were taken in April 2000 and July 2001 at five sites of the lake and were analysed with traditional methods as well as with tools of molecular biology (16S rDNA sequencing). These investigations have shown that (i) The original mosaic structure of the lake disappeared; periphytic algae became spatially uniform both in terms of taxonomic composition and abundance. (ii) The biodiversity of the reed periphyton decreased. The dominance of the weed algal species Achnanthes minutissima Kütz. increased significantly. (iii) The most frequent bacteria were members of the genera Pseudomonas, Acinetobacter, Shewanella and Agrobacterium characterised by oxidative chemoorganotrophic heterotrophic- and Aeromonas and Bacillus species with fermentative metabolism. (iv) Among the studied bacterial strains both plant growth promoting bacteria, members of Pseudomonas fluorescens group, and potential plant pathogens (Agrobacterium, Aureobacterium, Curtobacterium) were present.

Phylogeny of six naviculoid diatoms based on 18S rDNA sequences

18S rDNA sequences of six Naviculaceae species [Amphora montana, Gomphonema parvulum, Eolimna minima (syn. Navicula minima), Eolimna subminuscula (syn. Navicula subminuscula), Navicula veneta and Phaeodactylum tricornutum] were determined in order to assess the monophyly of this important group of diatoms, to date not included in 18S rDNA databases, and also that of the recently described genus Eolimna. Phylogenetic trees were constructed using other known diatom 18S rDNA sequences, and best tree topologies obtained were tested against alternative trees for their reliability. The analyses do not reject the monophyly of Naviculaceae and strongly support the separation of the genus Eolimna from Navicula sensu lato. The two species of Eolimna, however, do not appear to be each others closest relatives among the species investigated: rather, E. subminuscula shows affinities to A. montana, and E. minima to P. tricornutum. A. montana, a species which it has been proposed should be transferred into a separate taxon from the other five species, was found to have grouped well within them in all analyses.

Biofilm Bacterial Communities Inhabiting the Cave Walls of the Buda Thermal Karst System, Hungary

The diversity of biofilm bacterial communities associated with cave walls of the Buda Thermal Karst System (BTKS) located in Hungary was studied by scanning electron microscopy and molecular cloning based on 16S rRNA genes. Samples from two sites, the Molnár János cave (MJB) and the Rudas-Török spring cave (RTB), respectively, were analyzed and compared. The presence of iron precipitates was typical at both study sites, despite the fact that the cell morphological structure of the biofilms observed by SEM was characteristically different. Clones analyzed from BTKS were found to belong to 10 common phyla (Thermodesulfobacteria, Chloroflexi, Nitrospirae, Chlorobi, Proteobacteria, Firmicutes, Actinobacteria, Planctomycetes, Bacteroidetes, Verrucomicrobia) within the domain Bacteria. Moreover, sequences related to Aquificeae, Acidobacteria and Gemmatimonadetes were exclusive to MJB, while Cyanobacteria were found in RTB only. The phylogenetic distribution of the dominant bacterial clones was quite dissimilar between the two sites. In the biofilm from MJB clones affiliated with Firmicutes, whereas in the RTB clones related to Deltaproteobacteria were found in the highest number. In addition, substantially larger numbers of clone sequences related to thermophilic bacteria were recovered from MJB. On the basis of sequences of known microorganisms corresponding to our clone sequences, it is assumed that aerobic as well as anaerobic iron and sulfur transformation performed by different bacterial communities might be important biogenic processes in both caves.

Chloroparva pannonica gen. et sp. nov. (Trebouxiophyceae, Chlorophyta) - a new picoplanktonic green alga from a turbid, shallow soda pan

Somogyi B., Felföldi T., Solymosi K., Makk J., Homonnay Z.G., Horváth G., Turcsi E., Böddi B., Márialigeti K. and Vörös L. 2011. Chloroparva pannonica gen. et sp. nov. (Trebouxiophyceae, Chlorophyta) – a new picoplanktonic green alga from a turbid, shallow soda pan. Phycologia 50: 1–10. DOI: 10.2216/10-08.1 We describe Chloroparva pannonica Somogyi, Felföldi & Vörös gen. et sp. nov., a new trebouxiophycean picoplanktonic alga isolated from a turbid, shallow soda pan in Hungary. The cells are spherical to oval, less than 2 µm in diameter, with simple ultrastructure typical to small green algae. Cells divide by autosporulation, forming two daughter cells per autosporangium. Cell wall structure consists of an outer trilaminar layer, an inner microfibrillar layer and an electron-transparent layer covering the plasma membrane. The trilaminar layer of the mother cell wall often persists around the autospores. Typical chlorophyte pigments have been found, including chlorophyll a and b and lutein as the dominant carotenoid. The main fatty acid was oleic acid. The phylogenetic position of the new chlorophyte confirms the proposal of a new genus within the Trebouxiophyceae. Based on its 18S rRNA gene sequence, this isolate is distantly related to Nannochloris eucaryotum UTEX 2502, Chlorella minutissima C-1.1.9 and C. minutissima SAG 1.80 (≤ 97.6% 18S rRNA gene pairwise similarities).

Microbiological investigation of an industrial ultra pure supply water plant using cultivation-based and cultivation-independent methods

Ultra pure waters (UPW), characterized by extremely low salt and nutrient concentrations, can suffer from microbial contamination which causes biofouling and biocorrosion, possibly leading to reduced lifetime and increased operational costs. Samples were taken from an ultra pure supply water producing plant of a power plant. Scanning electron microscopic examination was carried out on the biofilms formed in the system. Biofilm, ion exchange resin, and water samples were characterized by culture-based methods and molecular fingerprinting (terminal restriction fragment length polymorphism [T-RFLP] analysis and molecular cloning). Identification of bacteria was based on 16S rDNA sequence comparison. A complex microbial community structure was revealed. Nearly 46% of the clones were related to as yet uncultured bacteria. The community profiles of the water samples were the most diverse and most of bacteria were recruited from bacterial communities of tube surface and ion exchange resin biofilms. Microbiota of different layers of the mixed bed ion exchange resin showed the highest similarity. Most of the identified taxa (dominated by β-Proteobacteria) could take part in microbially influenced corrosion.

Silver- and sulfadiazine-loaded nanostructured silica materials as potential replacement of silver sulfadiazine

Silver sulfadiazine (AgSD) is the leading topical antibacterial agent for the treatment of burn wound infections. Antibacterial effect of AgSD is limited by its poor aqueous solubility, and antibacterial activity develops only by decomposition of AgSD to silver ions and sulfadiazine. In this study, it is for the first time that application of silver-modified nanoporous silica carriers (MCM-41 or SBA-15) loaded with sulfadiazine (SD), instead of silver sulfadiazine, overcoming the abovementioned disadvantages has been demonstrated. By direct or post synthesis methods, 5-15 nm sized silver nanoparticles can be stabilized in the channels or on the outer surface of nanoporous silica supports; moreover, the empty channels can be loaded by SD molecules. The SD-loaded, silver-modified materials show sustained release properties and similar or even better antimicrobial properties than AgSD. Adsorption of AgSD on nanoporous silica particles significantly improves its water solubility.

Cellulomonas phragmiteti sp. nov., a cellulolytic bacterium isolated from reed (Phragmites australis) periphyton in a shallow soda pond

An alkalitolerant and moderately halophilic strain, designated KB23(T), characterized by optimal growth at pH 8.0-9.0 and in the presence of 5-7 % (w/v) NaCl, was isolated from a reed (Phragmites australis) periphyton sample originating from an extremely shallow, alkaline soda pond located in Hungary. Cells of strain KB23(T) were Gram-stain-positive, motile straight rods. Strain KB23(T) was facultatively anaerobic, catalase-positive, oxidase-negative and contained peptidoglycan type A4β (L-Orn-D-Asp). MK-9(H4) was the predominant isoprenoid quinone and anteiso-C(15 : 0), C(16 : 0) and anteiso-C(15 : 1) were the major cellular fatty acids. The DNA G+C content of strain KB23(T) was 74.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that this strain belongs to the genus Cellulomonas and that it is related most closely to Cellulomonas flavigena DSM 20109(T) (97.35 % similarity), Cellulomonas terrae DB5(T) (96.81 %), Cellulomonas iranensis O(T) (96.75), Cellulomonas chitinilytica X.bu-b(T) (96.60 %), Cellulomonas persica I(T) (96.53 %), Cellulomonas composti TR7-06(T) (96.45 %), Cellulomonas biazotea DSM 20112(T) (96.34 %) and Cellulomonas fimi DSM 20113(T) (96.20 %). According to these results, together with DNA-DNA hybridization and physiological data, strain KB23(T) is considered to represent a novel species of the genus Cellulomonas, for which the name Cellulomonas phragmiteti sp. nov. is proposed. The type strain is KB23(T) ( = DSM 22512(T)  = NCAIM B002303(T)).

Diversity and morphological structure of bacterial communities inhabiting the Diana-Hygieia Thermal Spring (Budapest, Hungary)

The Buda Thermal Karst System is an active hypogenic karst area that offers possibility for the analysis of biogenic cave formation. The aim of the present study was to gain information about morphological structure and genetic diversity of bacterial communities inhabiting the Diana-Hygieia Thermal Spring (DHTS). Using scanning electron microscopy, metal accumulating and unusual reticulated filaments were detected in large numbers in the DHTS biofilm samples. The phyla Actinobacteria, Firmicutes and Proteobacteria were represented by both bacterial strains and molecular clones but phyla Acidobacteria, Chlorobi, Chlorofexi, Gemmatimonadetes, Nitrospirae and Thermotogae only by molecular clones which showed the highest similarity to uncultured clone sequences originating from different environmental sources. The biofilm bacterial community proved to be somewhat more diverse than that of the water sample and the distribution of the dominant bacterial clones was different between biofilm and water samples. The majority of biofilm clones was affiliated with Deltaproteobacteria and Nitrospirae while the largest group of water clones was related to Betaproteobacteria. Considering the metabolic properties of known species related to the strains and molecular clones from DHTS, it can be assumed that these bacterial communities may participate in the local sulphur and iron cycles, and contribute to biogenic cave formation.

Arenimonas subflava sp. nov., isolated from a drinking water network, and emended description of the genus arenimonas

A strain designated PYM3-14T was isolated from the drinking water network of Budapest (Hungary) and was studied by polyphasic taxonomic methods. The straight-rod-shaped cells stained Gram-negative, were aerobic and non-motile. Phylogenetic analysis of the 16S rRNA gene sequence of strain PYM3-14T revealed a clear affiliation with members of the family Xanthomonadaceae within the class Gammaproteobacteria. The 16S rRNA gene sequence of strain PYM3-14T showed the closest sequence similarities to Arenimonas daechungensis CH15-1T (96.2 %), Arenimonas oryziterrae YC6267T (95.2 %) and Lysobacter brunescens UASM DT (94.4 %). The DNA G+C content of strain PYM3-14T, measured by two different methods (52.0 mol% and 55.9 mol%, respectively), was much lower than that of any member of the genus Arenimonas. The predominant fatty acids (>8 %) were iso-C16:0, iso-C15:0, iso-C14:0, iso-C17:1ω9c and C16:1ω7c alcohol. Strain PYM3-14T contained Q-8 as the major ubiquinone and phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and phosphatidylmonomethylethanolamine as the major polar lipids. According to phenotypic and genotypic data strain PYM3-14T represents a novel species of the genus Arenimonas, for which the name Arenimonas subflava sp. nov. is proposed. The type strain is PYM3-14T ( = NCAIM B 02508T = DSM 25526T). On the basis of new data obtained in this study, an emended description of the genus Arenimonas is also proposed.

Phylogenetic Diversity of Bacterial Communities Associated with Sulfurous Karstic Well Waters of a Hungarian Spa

The composition of bacterial communities associated with waters of one thermal and three sulfurous lukewarm wells of cavernous limestone aquifers in the Southwestern part of Hungary was studied in 2007 and 2008 by microscopy and culture-independent clone library analysis targeting the 16S rRNA gene. The presence of Thiothrix-like filamentous bacteria was observed by microscopy in the lukewarm samples. From the clone libraries, a high proportion of phylotypes belonging to Proteobacteria (Rhodobacter, Sphingopyxis, Phenylobacterium, Ochrobactrum, Methylobacterium, Sulfuritalea, Thiobacillus, Limnobacter, Acidovorax, Xanthomonadaceae, Thiothrix, Lysobacter, Pseudoxanthomonas, Desulfopila, Desulfocapsa, Desulforhopalus, Sulfuricurvum, Sulfurimonas, Sulfurospirillum) was revealed. In addition, phylotypes of Acidobacteria, Chloroflexi, Sphingobacteria, Clostridia, Aquificae, Deferribacteres and Chlorobi were detected. On the basis of their habitat preference 21 out of a total of 39 different phylotypes represented mesophilic and thermophilic sulfur bacteria. From the lukewarm samples large numbers of clones were affiliated with uncultured Epsilonproteobacteria clones common in sulfurous hydrothermal vents. From the thermal sample, several clones were in the closest relationship to the Sulfuritalea hydrogenivorans, a novel sulfur-oxidizing Betaproteobacterium.