Bohunická, Markéta

Abstract Numerous cyanobacterial strains previously identified as Scytonema hyalinum were determined to be phylogenetically distant from the type species of Scytonema, S. hofmannii . Morphological and molecular evidence suggests this distinct clade necessitates placement in a new genus, and we have described Kalymmatonema gen. nov. herein. Kalymmatonema has been demonstrated to exhibit five ribosomal operons, all of which differed in both sequence and secondary structure of conserved helical domains in the 16S–23S internal transcribed spacer rRNA region. Four of these operon copies were highly similar in 16S and 23S rRNA gene sequences, whereas the divergent fifth copy is thought to represent a whole‐operon horizontal gene transfer event. Through in‐depth analysis, we were able to recognize seven species new to science, the type species K. desertorum sp. nov., K. arcangelii comb. nov., K. chimaera sp. nov., K. ethiopiense sp. nov., K. gypsitolerans sp. nov., K. mateoae sp. nov., and K. oahuense sp. nov. We also created the new combination, K. hyalinum comb. nov., in order to include the original Scytonema hyalinum in this new genus based upon the common morphological feature of a mucilaginous apical cap on the trichomes. Kalymmatonema displays a complex evolution of its ribosomal operons, with evidence not only of horizontal gene transfer but also of internal rearrangements and mobile genetic elements that have transposed the tRNA‐containing region of the ITS rRNA region among the four similar operons. Additional investigation of the evolutionary history of this interesting genus will likely lead to a better understanding of the processes shaping ribosomal evolution in cyanobacteria.

‘Candidatus Phytoplasma spp.’ are pathogenic bacteria that infect many plant species. ‘Candidatus Phytoplasma pyri’, one of the members of the 16SrX group causes pear decline disease that adversely affects pear crops. To describe the prevalence of ‘Ca. P. pyri’ genotypes in the Czech Republic, 143 pear samples were collected from 41 locations including commercial orchards as well as trees along roads. Phytoplasma was detected by PCR in 115 samples, and it was possible to determine imp gene genotype in 84 samples. The most frequent genotypes were A1, B1, and C, which were identified in 71% of phytoplasma positive samples. ‘Ca. P. pyri’ was present either alone or as a mix of two populations in 88% of genotyped samples, and in another 6% of samples it was found in a mixed infection with ‘Ca. Phytoplasma mali’. A sole infection with ‘Ca. Phytoplasma mali’ was observed in 6% of samples. As for symptoms, 19% of symptomatic samples were found to be phytoplasma negative, and 74% of asymptomatic samples proved to be phytoplasma positive; leaf roll was more often observed in phytoplasma positive samples, while leaf narrowing rather indicated the absence of phytoplasma. The mildest symptoms were observed in samples infected with ‘Ca. P. pyri’ of the A1 imp genotype.

A total of 48 strains of thin, filamentous cyanobacteria in Synechococcales were studied by sequencing 16S rRNA and rpoC1 sequence fragments. We also carefully characterized a subset of these by morphology. Phylogenetic analysis of the 16S rRNA gene data using Bayesian inference of a large Synechococcales alignment (345 OTU’s) was in agreement with the phylogeny based on the rpoC1 gene for 59 OTU’s. Both indicated that the large family-level grouping formerly classified as the Leptolyngbyaceae could be further divided into four family-level clades. Two of these family-level clades have been recognized previously as Leptolyngbyaceae and Prochlorotrichaceae. Oculatellaceae fam. nov. and Trichocoleaceae fam. nov. are proposed for the other two families. The Oculatellaceae was studied in greater detail, and six new genera containing 14 species were characterized and named. These new taxa are: Pegethrix botrychoides, P. olivacea, P. convoluta, P. indistincta, Drouetiella lurida, D. hepatica, D. fasciculata, Cartusia fontana, Tildeniella torsiva, T. nuda, Komarkovaea angustata, Kaiparowitsia implicata, Timaviella obliquedivisa, and T. radians.