Survival of Mycobacterium avium in drinking water biofilms as affected by water flow velocity, availability of phosphorus, and temperature

Mycobacterium avium is a potential pathogen occurring in drinking water systems. It is a slowly growing bacterium producing a thick cell wall containing mycolic acids, and it is known to resist chlorine better than many other microbes. Several studies have shown that pathogenic bacteria survive better in biofilms than in water. By using Propella biofilm reactors, we studied how factors generally influencing the growth of biofilms (flow rate, phosphorus concentration, and temperature) influence the survival of M. avium in drinking water biofilms. The growth of biofilms was followed by culture and DAPI (4',6'-diamidino-2-phenylindole) staining, and concentrations of M. avium were determined by culture and fluorescence in situ hybridization methods. The spiked M. avium survived in biofilms for the 4-week study period without a dramatic decline in concentration. The addition of phosphorus (10 microg/liter) increased the number of heterotrophic bacteria in biofilms but decreased the culturability of M. avium. The reason for this result is probably that phosphorus increased competition with other microbes. An increase in flow velocity had no effect on the survival of M. avium, although it increased the growth of biofilms. A higher temperature (20 degrees C versus 7 degrees C) increased both the number of heterotrophic bacteria and the survival of M. avium in biofilms. In conclusion, the results show that in terms of affecting the survival of slowly growing M. avium in biofilms, temperature is a more important factor than the availability of nutrients like phosphorus.     

Microbial Respiration in Arctic Upland and Peat Soils as a Source of Atmospheric Carbon Dioxide

Knowledge on soil microbial respiration (SMR) rates and thus soil-related CO₂ losses from Arctic soils is vital because of the crucial importance of this ecosystem within the global carbon (C) cycle and climate system. Here, we measured SMR from various habitats during the growing season in Russian subarctic tundra by applying two different approaches: ¹⁴C partitioning approach and root trenching. The variable habitats encompassed peat and mineral soils, bare and vegetated surfaces and included both dry and moist ones. The field experiment was complemented by laboratory studies to measure bioavailability of soil carbon and identify sources of CO₂. Differences in bioavailability of soils, measured in the laboratory as basal soil respiration rates, were generally greater than inter-site differences in SMR rates measured in situ, suggesting secondary constraints at field conditions, such as soil C content. There was a tendency towards lower SMR in vegetated peat plateaus compared to upland mineral tundra (on average 137 vs. 185 g CO₂ m^?2 growing season^?1, respectively), but no significant differences were found. Surprisingly, the bare surfaces (peat circles) with 3500-year-old C at the surface exhibited about the largest SMR among all sites as shown by both methods. This was related to the general development of peat plateaus in the region, and uplifting of deeper peat with high C content to the surface during the genesis of peat circles. This observation is particularly relevant for decomposition of deeper peat in vegetated peat plateaus, where soil material similar to the bare surfaces can be found. The data indicate that the large stocks of C stored in permafrost peatlands are principally available for decomposition despite old age.     

Selected ion monitoring in quantitative gas-liquid chromatographic-mass spectrometric detection of fatty acid methyl esters from environmental samples

To calculate selected ion monitoring (SIM) gas-liquid chromatography (GLC)-mass spectrometry (MS) results of phospholipid fatty acids (PLFAs) from environmental samples, coefficients were calculated for each fatty acid by dividing the sum of ion intensities in SCAN with that of ions followed in SIM. The SIM chromatogram areas were multiplied with the coefficients, and then processed as in SCAN. The results were compared to those obtained using calibration curves and SCAN. The calibration curve and coefficient based results had the greatest errors of 7.8 and 6.7%, respectively, outside standard deviations of SCAN percentages. The PLFA contents calculated using calibration curves and coefficients were 104.9+/-7.3% and 101.5+/-8.6%, respectively, of SCAN values. SIM increased sensitivity approximately 10-fold from SCAN, and the smallest detectable injected amount was approximately 50 ng (0.18 nmol) for 20 fatty acids, corresponding to 4 x 10(6) cells.     

Proxy comparison in ancient peat sediments: pollen,macrofossil and plant DNA

We compared DNA, pollen and macrofossil data obtained from Weichselian interstadial (age more than 40 kyr) and Holocene (maximum age 8400 cal yr BP) peat sediments from northern Europe and used them to reconstruct contemporary floristic compositions at two sites. The majority of the samples provided plant DNA sequences of good quality with success amplification rates depending on age. DNA and sequencing analysis provided five plant taxa from the older site and nine taxa from the younger site, corresponding to 7% and 15% of the total number of taxa identified by the three proxies together. At both sites, pollen analysis detected the largest (54) and DNA the lowest (10) number of taxa, but five of the DNA taxa were not detected by pollen and macrofossils. The finding of a larger overlap between DNA and pollen than between DNA and macrofossils proxies seems to go against our previous suggestion based on lacustrine sediments that DNA originates principally from plant tissues and less from pollen. At both sites, we also detected Quercus spp. DNA, but few pollen grains were found in the record, and these are normally interpreted as long-distance dispersal. We confirm that in palaeoecological investigations, sedimentary DNA analysis is less comprehensive than classical morphological analysis, but is a complementary and important tool to obtain a more complete picture of past flora.     

Age-dependent increase in the non-specific cholinesterase activity of the capillaries in the rat neostriatum

Summary Histochemically demonstrable non-specific cholinesterase activity in the capillaries of the neostriatum of 3–5-month-old rats was much weaker than that of 24–27-month-old rats. In the young adult rats the activity was electron microscopically localized mainly in endoplasmic reticulum and perinuclear cisternae of the endothelial cells, while capillaries of old rats showed a positive reaction also in the basal lamina and outer cell membranes of glial processes.     

Optimal Regulation of Gas Exchange: Evidence from Field Data

Since the work of Cowan in 1977 it has been assumed that plantsregulate their stomata in a way that maximizes photosynthesisat a constant average rate of transpiration. The approach wasfurther developed by Hari et al. (1986) by introducing additionalassumptions which enabled the mathematical solution of the optimizationproblem using the Lagrangian method. The solution is testedfor Scots pine seedlings against field data. The results supportthe optimization hypothesis.Copyright 1993, 1999 Academic Press Pinus sylvestris (L.), stomatal conductance, photosynthesis, transpiration, optimization, field measurements, mathematical model, Lagrangian method     

Finding a common ordination for several data sets by individual differences scaling

Individual differences scaling is a multidimensional scaling method for finding a common ordination for several data sets. An individual ordination for each data set can then be derived from the common ordination by adjusting the axis lengths so as to maximize the correlations between observed proximities and individual ordination distances. The importance of the various axes for each data set and the mutual similarities and goodness of fit for the individual data sets are described by weight plots. As an example, 46 soft-water lakes in eastern Finland are ordinated on two dimensions according to 3 chemical data sets (water in summer and autumn, sediment) and 4 biological sets (major phytoplankton groups, phytoplankton, surface sediment diatom and cladoceran assemblages). The method seems to be effective as a means of ordination for obtaining the common ordination for the data sets. The major taxonomic groups gave the ordination which differed most clearly from the ordinations of the other data sets. Phytoplankton was most poorly ordinated in all the analyses. The other data sets were fairly coherent. When only biological data sets were ordinated, the diatoms and cladocerans showed rather different patterns. It seems that the cladocerans are best correlated with water chemistry, both according to weights in the joint analysis, and according to correlation between the axes from the biological data sets and the chemical variables.Abbreviations CCA = Canonical correspondence analysis - IDS = Individual differences scaling - MDS = multidimensional scaling - PCA = Principal components analysis