Aeromonas spp.-mediated cell-contact cytotoxicity is associated with the presence of type III secretion system

In the study we examined the production of cytotonic and cytotoxic toxins and the presence of a type III secretion system (TTSS) in 64 Aeromonas spp. strains isolated from fecal specimens of patients with gastroenteritis. We observed that contact of the bacteria with host epithelial cells is a prerequisite for their cytotoxicity at 3 h incubation. Cell-contact cytotoxic activity of the strains was strongly associated with the presence of the TTSS. Culture supernatants of the strains induced low cytotoxicity effects at the same time of incubation. Cell-free supernatants of 61 (95%) isolates expressed cytotoxic activity which caused the destruction of HEp-2 cells at 24 h. Moreover, 44% strains were cytotonic towards CHO cells and 46% of strains invaded epithelial cells.     

PHYLOGENY AND SYSTEMATICS OF THE GENUS MONOMORPHINA (EUGLENACEAE) BASED ON MORPHOLOGICAL AND MOLECULAR DATA1

Morphological studies of 16 strains belonging to the genus Monomorphina revealed a single, parietal, orbicular chloroplast in their cells. The chloroplast has a tendency to be perforated and disintegrates in aging populations and thus may appear to be many chloroplasts under the light microscope. A single chloroplast in the cells of Cryptoglena skujae is also parietally located and highly perforated. It never forms a globular and closed structure, but is open from the side of the furrow, resembling the letter C. We have verified the Monomorphina pyrum group (M. pyrum–like) on the basis of phylogenetic analysis of SSU rDNA and morphological data. The strain CCAC 0093 (misidentified as M. reeuwykiana) diverges first on the SSU rDNA phylogenetic tree. The rest of the M. pyrum–like strains form a tight cluster, subdivided into several smaller ones. Because morphological differences between the M. pyrum–like strains (including the strain CCAC 0093) do not conform to the tree topology, we suggest that they all (except the strain CCAC 0093) belong to M. pyrum. We designate a new species, M. pseudopyrum, for the strain CCAC 0093, solely on the basis of molecular characters. We also suggest that M. reeuwykiana and similar species should stay in Phacus and Lepocinclis unless detailed molecular and morphological studies show otherwise. Emended diagnoses of the genera Monomorphina and Cryptoglena and the species M. aenigmatica are also proposed, as well as the delimitation of an epitype for M. pyrum, the type species for the genus Monomorphina.     

Morphological and molecular examination of relationships and epitype establishment of Phacus pleuronectes,Phacus orbicularis,and Phacus hamelii1

Verification of morphological diagnostic features and the establishment of three epitypes for three species of Phacus Dujardin—Phacus pleuronectes (O. F. Müll.) Dujardin, Phacus orbicularis Hübner, and Phacus hamelii Allorge et Lefèvre—was performed based on literature studies and analysis of morphological (cell shape, cell size, and periplast ornamentation) as well as molecular (18S rDNA) characters. Periplast ornamentation was recognized as a main diagnostic character, distinguishing P. orbicularis from P. pleuronectes and P. hamelii. Phacus orbicularis has struts running perpendicular to the longitudinal axis of the strips, while P. pleuronectes and P. hamelii do not. On the SSU rDNA tree, obtained by the Bayesian method, P. orbicularis, P. pleuronectes, and P. hamelii belong to three distinct clades. Some of the phylogenetic relationships are not resolved, but there are at least three Phacus species (P. hamatus, P. platyaulax, P. longicauda; for taxonomic authors, see Introduction) that are more closely related to P. orbicularis than is P. pleuronectes. Phacus hamelii is more closely related to P. ranula and the assemblage of several species of Phacus, which have small cells, than to P. orbicularis or P. pleuronectes.     

In vitro virulence characteristics of rare serovars of <Emphasis Type="Italic">Salmonella enterica</Emphasis> isolated from sand lizards (<Emphasis Type="Italic">Lacerta agilis</Emphasis> L.)

The aim of this study was to estimate virulence potential of Salmonella enterica strains colonizing the gut of free-living sand lizards (Lacerta agilis L.). The strains belonged to three Salmonella serovars: Abony, Schleissheim, and Telhashomer. Adhesion and invasion abilities of the strains were determined in quantitative assays using the gentamicin protection method. Induction of apoptosis was assessed using HeLa cell monolayers. PCR assays were used for detection of 26 virulence genes localised within mobile elements: pathogenicity islands, virulence plasmids, and prophage sequences. In vitro studies revealed that all strains had adhesion and invasion abilities to human epithelial cells. The isolates were cytotoxic and induced apoptosis of the cells. The serovars differed in the number of virulence-associated genes: up to 18 genes were present in Salmonella Schleissheim, 17 in Salmonella Abony, whereas as few as six genes were found in Salmonella Telhashomer. Generally, Salmonella Abony and Salmonella Schleissheim did not differ much in gene content connected with the presence SPI-1 to -5. All of the strains lacked genes localised within bacteriophages and plasmids. The presence of virulence-associated genes and in vitro pathogenicity assays suggest that Salmonella sp. strains originating from autochthonous, free-living lizards can potentially infect and cause disease in humans.     

Effect of climate change on sporulation of the teleomorphs of <Emphasis Type="Italic">Leptosphaeria</Emphasis> species causing stem canker of brassicas

Leptosphaeria maculans and L. biglobosa are closely related sibling fungal pathogens that cause phoma leaf spotting, stem canker (blackleg) and stem necrosis of oilseed rape (Brassica napus). The disease is distributed worldwide, and it is one of the main causes of considerable decrease in seed yield and quality. Information about the time of ascospore release at a particular location provides important data for decision making in plant protection, thereby enabling fungicides to be used only when necessary and at optimal times and doses. Although the pathogens have been studied very extensively, the effect of climate change on the frequencies and distributions of their aerially dispersed primary inoculum has not been reported to date. We have collected a large dataset of spore counts from Poznan, located in central-west part of Poland, and studied the relationships between climate and the daily concentrations of airborne propagules over a period of 17 years (1998–2014). The average air temperature and precipitation for the time of development of pseudothecia and ascospore release (July–November), increased during the years under study at the rates of 0.1 °C and 6.3 mm per year. The day of the year (DOY) for the first detection of spores, as well as the date with maximum of spores, shifted from 270 to 248 DOY, and from 315 to 265 DOY, respectively. The acceleration of the former parameter by 22 days and the latter by 50 days has great influence on the severity of stem canker of oilseed rape.