Sequential colonization by river periphyton analysed by microscopy and molecular fingerprinting

1. An artificial glass substratum was incubated in the River Danube for a period of 28 days in order to detect the sequential colonization of microorganisms.
2. Light and fluorescent microscopy showed that microalgae and the picoalgal fraction on the slides increased rapidly over the first 2 weeks of colonization. Diatoms were numerically the most abundant component of the periphyton and their species richness and diversity increased rapidly in the early phase of colonization whereas diversity subsequently increased moderately.
3. Evenness of the diatom community was initially high, lower in the intermediate phase and again higher later on. Succession involving early, intermediate and late colonizer species was observed. Community composition during the first 5 days of colonization was very different from later stages whereas there were only minor changes subsequently.
4. Molecular community analysis by means of terminal restriction fragment length polymorphism analysis of PCR amplified 16S rRNA and 18S rRNA genes pointed to even larger differences between the composition of samples obtained early and late in the period.
5. The number of 18S rRNA and 16S rRNA terminal restriction fragments (T-RF-s) was variable over the colonization period and the fragment patterns of both the bacterial and eukaryotic portion of the microbial community were variable, with most T-RF-s unique to a single sample, suggesting a wide diversity and dynamic properties of periphytic organisms.     

Fluorescence microscopy of mycobacteria in pleural effusions

The diagnostic advantage of fluorescence microscopy (FM) of Papanicolaou-stained cytological specimens obtained by bronchoscopy has been described previously. This study was designed to evaluate the method's diagnostic benefit in cytological preparations of pleural effusions in cases of active pulmonary tuberculosis. In contrast to bronchial material there is no advantage in cytological evaluation of pleural effusions by FM.     

Growth hormone-induced effects on mortality, energy status and growth: a field study on Brown Trout (Salmo trutta)

1. Growth hormone (GH) treatment increases the growth rate and competitive ability of salmonids under laboratory conditions. Since fast growth should increase fitness, why is endogenous secretion of GH not higher in wild fish? To address this question, three hypotheses were suggested. H₁: high GH levels reduce antipredator responses and may therefore increase mortality from predation. H₂: high GH levels reduce long-term (e.g. over winter) survival by reducing allocation to critical energy reserves. H₃: GH is not beneficial for growth under natural conditions.
2. To test these hypotheses, the performance of GH-treated juvenile Brown Trout ( Salmo trutta ) and control (placebo) trout was compared in an enclosed stream section subjected to natural predation. Four experiments were conducted during winter, spring, summer and autumn, respectively.
3. Mortality rates were not significantly different between GH-treated and control trout in any of the four experiments so H₁ was not supported. Energy reserves were generally lower in GH-treated fish, which is consistent with H₂, whereas growth rates in mass were higher in GH-treated fish than in controls so H₃ was not supported. This suggests that GH promotes growth at the expense of investment in maintenance.
4. Judging from growth and mortality rates, the fitness of GH-treated and control trout appeared similar. Thus, escaped GH-manipulated fish may compete successfully with wild fish.
5. Hatchery-raised trout with higher initial condition index suffered higher mortality rates than more slender fish. This novel finding may be explained by reduced escape ability related to body morphology, reduced behavioural responses towards predators by high-condition trout, or predator preferences for high-condition fish.     

Interactions of Cd with Zn, Cu, Mn and Fe for lettuce (Lactuca sativa L.) in hydroponic culture

Abstract. The effect and accumulation of cadmium (Cd) in lettuce grown by means of the hydroponic technique was investigated by multivariate analysis, and was found to be affected by the concentration of other trace elements. Particularly iron acted in a strongly antagonistic way against Cd. Consequently, no absolute toxicity limits for Cd can be drawn without considering other trace elements.     

Radiation-induced improvement of the freeze-resistance of a cold-sensitive wheat variety: Freeze-tolerance and fatty acid patterns

Effects of 3–15 krad ⁶⁰Co gamma radiation on cereal seeds were investigated with regard to the frost hardiness of leaves of 5–7-day-old seedlings. Comparative studies were carried out on the gas-chromatographically determined distribution patterns of fatty acids in different pools (total fatty acid, total lipid, polar lipids) of a cold-resistant (cv. Mironowskaya 808) and a cold-sensitive (cv. Penjamo 62) cultivar of wheat (Triticum aestivum L.). Parallelism between fatty acid distribution pattern, empirical parameters suggested for quantitative measures of cold tolerance (the ratio unsat/sat and double-bond index), and the low-temperature behaviour of shoots grown from radiation treated seeds of ‘Penjamo 62’, was also examined. To monitor differences in the fatty acid syntheses of ‘Mironowskaya 808’and ‘Penjamo 62’, and to demonstrate radiation-induced changes in fatty acid turnover a [1–¹⁴C]-acetate incorporation technique was employed. The results of practical importance are: 1. A significant improvement in the frost-resistance of the cold-sensitive ‘Penjamo 62’variety could be achieved with 6–9 krad irradiation, the half-freeze-killing temperature dropping from ?6 to about ?18°C. 2. Freeze-hardiness, no matter whether inherited or gained, could be abolished by gamma irradiation with higher dose. The following conclusions of theoretical interest can be drawn: 1. Low-temperature behaviour of plant tissues is a dynamic property rather than a static one, not only the formation but also the breakdown of certain hydrocarbon chains may be of paramount relevance in cold-tolerance. 2. Not the linolenic (18:3) component, but rather the overall distribution pattern of the C₁₈ family seems to correlate with low-temperature-responses of shoots. 3. Empirical parameters investigated do not provide reliable quantitative measures of the susceptibility to freeze (and cold-) injuries. 4. Changes in the syntheses of some key proteins (e.g. peroxidase, water-soluble proteins, etc.) may also be important in adaptation to low-temperature conditions.     

Hardiness dependent accumulation of phospholipids in leaves of wheat cultivars

Phospholipid content and composition in the leaves of thirteen cultivars of wheat differing in frost hardiness, were compared before and after hardening in order to see whether phospholipids play a role in surviving at low temperatures. The content of phospholipids in the leaves at the end of the hardening could be related to the aquired hardiness, and the relationship between the two phenomena could be described by the regression equation y = (0.174 ± 0.0016) x + 1311. Accumulation of phospholipids represents a hardiness dependent augmentation of membranes. Phosphatidylcholine appeared to be preferentially accumulated in hardy cultivars during the hardening process. As there are no significant differences in phospholipid fatty acid compositions investigated earlier, these results suggest the importance of the polar head group composition of membranes in avoiding frost injury.