49 research outputs found
Fungal microbiota from rain water and pathogenicity of Fusarium species isolated from atmospheric dust and rainfall dust
In order to determine the presence of Fusarium spp. in atmospheric dust and rainfall dust, samples were collected during September 2007, and July, August, and October 2008. The results reveal the prevalence of airborne Fusarium species coming from the atmosphere of the South East coast of Spain. Five different Fusarium species were isolated from the settling dust: Fusarium oxysporum, F. solani, F. equiseti, F. dimerum, and F. proliferatum. Moreover, rainwater samples were obtained during significant rainfall events in January and February 2009. Using the dilution-plate method, 12 fungal genera were identified from these rainwater samples. Specific analyses of the rainwater revealed the presence of three species of Fusarium: F. oxysporum, F. proliferatum and F. equiseti. A total of 57 isolates of Fusarium spp. obtained from both rainwater and atmospheric rainfall dust sampling were inoculated onto melon (Cucumis melo L.) cv. Piñonet and tomato (Lycopersicon esculentum Mill.) cv. San Pedro. These species were chosen because they are the main herbaceous crops in Almeria province. The results presented in this work indicate strongly that spores or propagules of Fusarium are able to cross the continental barrier carried by winds from the Sahara (Africa) to crop or coastal lands in Europe. Results show differences in the pathogenicity of the isolates tested. Both hosts showed root rot when inoculated with different species of Fusarium, although fresh weight measurements did not bring any information about the pathogenicity. The findings presented above are strong indications that long-distance transmission of Fusarium propagules may occur. Diseases caused by species of Fusarium are common in these areas. They were in the past, and are still today, a problem for greenhouses crops in AlmerÃa, and many species have been listed as pathogens on agricultural crops in this region. Saharan air masses dominate the Mediterranean regions. The evidence of long distance dispersal of Fusarium spp. by atmospheric dust and rainwater together with their proved pathogenicity must be taken into account in epidemiological studies
Temporal variability and effect of environmental variables on airborne bacterial communities in an urban area of Northern Italy
Despite airborne microorganisms representing a relevant
fraction of atmospheric suspended particles, only a small
amount of information is currently available on their abundance
and diversity and very few studies have investigated the environmental
factors influencing the structure of airborne bacterial
communities. In this work, we used quantitative PCR and Illumina
technology to provide a thorough description of airborne
bacterial communities in the urban area of Milan (Italy). Forty
samples were collected in 10-day sampling sessions, with one
sessionper season.Themeanbacterialabundancewasabout104
ribosomal operons perm3 of air andwas lower inwinter than in
the other seasons. Communitieswere dominated by Actinobacteridae,
Clostridiales, Sphingobacteriales and fewproteobacterial
orders (Burkholderiales, Rhizobiales, Sphingomonadales
andPseudomonadales).Chloroplastswere abundant in all samples.
Ahigher abundanceof Actinobacteridae,which are typical
soil-inhabiting bacteria, and a lower abundance of chloroplasts in samples collected on cold days were observed. The variation
in community composition observed within seasons was comparable
to that observed between seasons, thus suggesting that
airborne bacterial communities showlarge temporal variability,
even between consecutive days. The structure of airborne bacterial
communities therefore suggests that soil and plants are the
sources which contribute most to the airborne communities of
Milan atmosphere, but the structure of the bacterial community
seems to depend mainly on the source of bacteria that predominates
in a given period of time
Diamagnetic levitation enhances growth of liquid bacterial cultures by increasing oxygen availability
Diamagnetic levitation is a technique that uses a strong, spatially-varying magnetic field to reproduce aspects of weightlessness, on the Earth. We used a superconducting magnet to levitate growing bacterial cultures for up to 18 hours, to determine the effect of diamagnetic levitation on all phases of the bacterial growth cycle. We find that diamagnetic levitation increases the rate of population growth in a liquid culture and reduces the sedimentation rate of the cells. Further experiments and microarray gene analysis show that the increase in growth rate is due to enhanced oxygen availability. We also demonstrate that the magnetic field that levitates the cells also induces convective stirring in the liquid. We present a simple theoretical model, showing how the paramagnetic force on dissolved oxygen can cause convection during the aerobic phases of bacterial growth. We propose that this convection enhances oxygen availability by transporting oxygen around the liquid culture. Since this process results from the strong magnetic field, it is not present in other weightless environments, e.g. in Earth orbit. Hence, these results are of significance and timeliness to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena