The disturbance and vegetation dynamics: a review and an alternative framework

Disturbances are common phenomena that occurs in nature and significantly affects the dynamics of vegetation and plant populations. This paper shows that despite considerable progress in the theory of disturbances, for different authors the notion of disturbance has different meanings. The differences follow from an alternative understanding of the term, assumption of the holistic or reductionistic concept of the study or different approaches to equilibrium and non-equilibrium in nature. Different theoretical and methodological assumptions taken when analysing vegetation changes under the effect of disturbances allow relative arbitrariness in the interpretation of results. However, not all biotic interactions and ecological processes taking place in plant communities can be identified as disturbances. The effects of disturbances should be described on the basis of an objective assessment of what is normal for the functioning and stabilisation of a community as well as what disturbs and disrupts this equilibrium. Moreover, assuming the equivalent treatment of ecological systems, the interaction of the disturbing factors should be related to a specific level of life organisation (an individual, population or community), which would permit unambiguous discernment of the disturbance effects and finally generalise its effects on different levels of the hierarchical structure of vegetation.     

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.     

A global view on fungal infections in humans and animals: opportunistic infections and microsporidioses

After cardiovascular diseases, infectious diseases are the second most common cause of death worldwide. Although these infections are caused mainly by viruses or bacteria, a systematically growing prevalence of human and animal opportunistic fungal infections is noticeable worldwide. More attention is being paid to this problem, especially due to the growing frequency of recalcitrant and recurrent mycoses. The latter are classically divided into superficial, which are the most common type, subcutaneous, and systemic. This work discusses opportunistic fungal pathogens without proven horizontal transmission between different animal species including humans and microsporidia as spore-forming unicellular parasites related to fungi; however, with a yet undetermined taxonomic position. The review also mentions aetiological agents, risk factors, epidemiology, geographical distribution, and finally symptoms characteristic for individual disease entities. This paper provides insight into fungal infections from a global perspective and simultaneously draws attention to emerging pathogens, whose prevalence is continuously increasing. Finally, this work also takes into consideration the correct nomenclature of fungal disease entities and the importance of secondary metabolites in the pathogenesis of fungal infections.