2016): Analysis of light quality and assemblage composition on diatom motility and accumulation rate, Diatom Research,The photosensitive nature of pennate diatom movement has long been observed, with cells being able to change the direction of their movement depending on the light conditions detected at the tips of the cells. However, much of this evidence is based on observations of cells in isolated, single-species culture, thus devoid of any information regarding inter-species interactions that might occur in more complex assemblages. In this study, we tested light-sensitive diatom motility responses (cell accumulation into light spots and high irradiation-induced direction change) in the absence and presence of other species. In the light spot accumulation assay, each species showed characteristic accumulation rates with regard to light irradiance, wavelength, and presence of other species. In mixed-species assemblages, the relative abundance of different species present in the light spot could be directly modified by changes in ambient light conditions. Diatom cells were also irradiated at their leading or trailing ends in the presence or absence of other diatom species to determine the effect of assemblage composition on high irradiance photo-responsiveness. While most multi-species combinations resulted in no significant change in the high irradiance response, Stauroneis phoenicenteron cells showed a significantly slower blue light stimulated direction change response, dependent on relative cell abundance in the presence of Craticula cuspidata. Our experiments thus indicate that the rate of irradiation-stimulated direction change and accumulation ability are not only species-specific and dependent on light wavelength and intensity, but can also be modulated by the presence of other diatom species.

BackgroundThe haemotropic mycoplasmas Mycoplasma haemofelis and Candidatus Mycoplasma haemominutum cause feline infectious anaemia with infection rates in feline populations reflecting widespread subclinical infection. Clinically significant infections are much rarer but can be life-threatening. Current diagnosis is dependent upon visualising organisms in stained blood smears, PCR or quantitative PCR (qPCR). These procedures are labour-intensive and time-consuming. Furthermore, PCR-based approaches offer limited insight into the disease burden of the infected animal.MethodsWe have developed a novel and rapid flow cytometric system that permits diagnosis of haemotropic mycoplasma infections and quantitation of the percentage of erythrocytes that are parasitized. The method exploits the fact that mature mammalian erythrocytes, the host cell for haemoplasmas, are enucleated and thus lack nucleic acid. DRAQ5 is a synthetic anthrocycline dye which rapidly crosses cell membranes and binds to nucleic acids. The presence of exogenous bacterial DNA in mammalian erythrocytes can, therefore, be detected by DRAQ5 uptake and flow cytometric detection of DRAQ5 fluorescence.ResultsHere, we show that this system can detect epi-erythrocytic infection of companion felines by haemotropic mycoplasma. Due to their differences in size, and hence the quantity of DNA, the two major feline hemoplasmas M. haemofelis and Candidatus M. haemominutum can be distinguished according to DRAQ5 fluorescence. We have also shown the usefulness of DRAQ5 uptake in monitoring a cat infected with M. haemofelis sequentially during treatment with doxycycline.ConclusionsThe technique described is the first report of a flow cytometric method for detecting haemotropic mycoplasmas in any species and could be applied to widespread screening of animal populations to assess infection by these epi-erythrocytic parasites.