Particle-Based Axenic Media for Tetrahymenids*

SYNOPSIS. Autoclavable, natural particulate media simplify axenic cultivation of tetrahymenid ciliates and presumably favor selection for phagotrophy. Viability is at least 2 months at room temperature (24–26 C) for the lipid-sensitive tetrahymenids Tetrahymena setosa, T. corlissi, T. paravorax, T. limacis, and T. patula, also for T. rostrata and (at 12 C), for strains of the T. pyriformis complex and Glaucoma chattoni. A typical medium consists of crude soy “lecithin”+ skim milk powder +Saccharomyces cerevisiae cells. Other useful particules readily available commercially are: whole liver powder, cells of Micrococcus lysodeikticus and Escherichia coli, and powdered residue of liver which had been extracted with 70% ethanol (liver #2). Preliminary experiments indicate that some of these media are suitable for the maintenance of Paramecium octaurelia stock 299S and Colpidium campylum. Such mixtures may serve as points of departure for devising media for more fastidious phagotrophs.     

Morphogenetic Responses to Gibberellic Acid of a Radiation-induced Mutant Dwarf in Groundsel, Senecio vulgaris L.

A dwarf mutant of Senecio vulgaris L. induced by gamma radiation,which differs from the wild-type by a single recessive gene,grew as tall as the wild-type plant, and almost five times astall as dwarf control plants when treated at weekly intervalsfrom the seedling stage with 10 p.p.m. gibberellic acid. Thewild-type groundsel responded only slightly to similar treatment.Some evidence was obtained that the response to GA was relativilygreater when plants were grown during the late autumn. Dwarfnessin the mutant is due to fewer as well as to shorter internodes;the rate of leaf initiation is reduced, but the onset of thereproductive phase and the duration of the life-cycle are notaffected by the mutation. Gibberellic acid leads to a conspicuouselongation of the internodes intreated dwarf plants, but notalways to a significant increase in their number. An increasein the dry weight of treated plants was observed, and this wasshown to be due to an increase in photosynthetic area and notto increased photosynthetic efficiency. Comparative observationsof shoot morphogenesis in wild-type and dwarf groundsel. andin dwarf treated with gibberellic acid, have shown that thetype of shoot development induced by gibberellic acid in dwarfplants does not correspond exactly to the normal mode of developmentin wild-type plants. Increased mitotic activity in the subapicaltissue of the mutant following gibberellic acid treatment resultedin greater and earlier elongation of the internodes. However,the typical form and dimensions of the wild-type plant werenot wholly restored.     

BACTERIOLOGICAL STUDIES OF IMMERSION CLEANING OF MILKING EQUIPMENT ON COMMERCIAL FARMS

SUMMARY: A study has been made of the immersion cleaning technique as applied on commercial farms. In an initial survey bacteriological results for rinses and swabs of the milking equipment were satisfactory on most farms, but on one farm the results were very disappointing. Further investigations at this farm showed that the poor results were caused partly by sporing bacteria which survived the caustic soda treatment, presumably in the spore state, and partly by non-sporing organisms, chiefly chromobacteria and micrococci.
These non-sporing organisms are found in abundance on the surface of dirty wash troughs, and under certain conditions re-contamination of the milking equipment can occur during the rinsing operation. Suggested modifications to the original immersion cleaning technique include the use of hot water for the before-milking hypochlorite rinse, brushing the equipment in the after-milking rinse to remove extraneous dirt, regular cleansing of the wash trough and the monthly cleansing of the basket and bin.     

MAGNITUDE ESTIMATION WITH AND WITHOUT RE-SCALING

Analysis of variance was applied to 3,107 magnitude estimations (ME) obtained upon 173 panelists (16 panels) evaluating the areas of 18 geometric figures. As Butler et al. (1987) pointed out, if a full ANOVA is applied to the values transformed to logarithms, there is no need to re-scale, i.e., normalize the values as is usually done. In fact, even with re-scaling, total variability is not accounted for adequately unless all the sources of variation are partitioned out in the analysis. Under some circumstances, re-scaling is needed: some laboratories re-scale to the arithmetic mean, others to the geometric one. The error was somewhat greater when the data were re-scaled to the arithmetic mean. The residuals of the ME values transformed to logarithms conformed essentially to a normal distribution. Kurtosis was greater, 5.30; otherwise the distribution was close to a log normal one. The average coefficient of variation was <10%.     

A Note on the Possible Ecological Significance of Chemotaxis in Certain Ciliated Protozoa1

ABSTRACT. A heat-stable chemoattractant has been isolated from bacterial cultures. This component has a molecular weight in the range of 500–1000 daltons, is produced by both Gram-positive and Gram-negative bacteria, and serves equally well as an attractant for both the bacterial feeding Paramecium and for its natural predator, Didinium. Aspects of the ecological relationship between bacterial feeding ciliates and their ciliate predators are briefly discussed with respect to responses of both predator and prey to such a common chemotactic bacterial factor.     

Effects of temperature and current discharge on the concentration and photosynthetic activity of the phytoplankton in the upper Mississippi River

SUMMARY. Temperature and current discharge regulated phytoplanktonic concentration, chlorophyll-a concentration, the light-saturated rate of photosynthesis (P_max), and photosynthetic capacity (P_cap) in the Mississippi River at Prairie Island, Minnesota. The chlorophyll-a maximum was 48 mg m⁻³ in 1975, a wet year with a high current discharge, and 190 mg m⁻³ in 1976, a relatively dry year. The highest values of P_max were 0.37 (mgO₂ I⁻¹h⁻¹) in 1975 and 1.60 in 1976. P_cap varied from 3 to 21 (gO₂ per g chlorophyll-a h⁻¹) both years, and its value was highly correlated with temperature. The temperature optimum shifted from 16°C for P_cap in the spring, to greater than 28°C in the summer. Multiple regression analysis indicated a second-order relationship of P_cap in the spring to temperature. Other independent variables explained only negligible variation of P_cap.     

Climatic factors influencing spore production in Alternaria brassicae and Alternaria brassicicola

Sporulation in A. brassicae and A. brassicicola on naturally-infected leaf discs of oilseed rape and cabbage required humidities equal to or higher than 91.5% and 87% r.h. respectively. The optimum temperatures for sporulation were 18–24°C for A. brassicae and 20–30°C for A. brassicicola at which temperatures both fungi produced spores in 12–14 h. Above 24°C sporulation in A. brassicae was inhibited. At sub-optimal temperatures sporulation times for A. brassicicola were significantly longer than for A. brassicae with the differences increasing with decrease in temperature. Interrupting a 16-h wet period at 20°C with a period of 2 h at 70% or 80% r.h. did not affect sporulation in either fungus but a dry interruption of 3–4 h inhibited sporulation in both. Exposure of both fungi to alternating wet (18 h at 100% r.h., 20°C) and dry periods (6 or 30 h at 5565% r.h., 20°C) did not affect the concentration of spores produced in each wet period. Sporulation times were not affected by either the host type of the age of the host tissue. White light (136 W/m²) inhibited sporulation in A. brassicae with the degree of inhibition increasing with increasing light intensity. The effect of light on sporulation in A. brassicicola was not tested.