No abstract

To evaluate the impact of environmental factors on the occurrence of environmental mycobacteria, viable counts of mycobacteria were measured in samples of brook water collected from 53 drainage areas located in a linear belt crossing Finland at 63°north latitude. The numbers of mycobacteria were correlated with characteristics of the drainage area, climatic parameters, chemical and physical characteristics of the water, and counts of other heterotrophic bacteria in the water. The numbers of mycobacteria in the water ranged from 10 to 2,200 CFU/liter. The counts correlated positively (P < 0.001) with the presence of peatlands, precipitation data, chemical oxygen demand, water color, and concentrations of Fe, Al, Cu, Co, and Cr. The mycobacterial counts correlated negatively (P < 0.001) with water pH, whereas other heterotrophic bacterial counts lacked any correlation with pH. A linear regression model with four independent variables (i.e., peatlands in the drainage area, chemical oxygen demand, concentration of potassium, and pH) explained 83% of the variation in mycobacterial counts in brook waters. Our results suggest that acidification may enhance the growth of environmental mycobacteria.

No abstract

E. IIVANAINEN, P.J. MARTIKAINEN, P. VÄ Ä NÄ NE N A N D M .-L . K AT I LA . 1999. The occurrence of mycobacteria was studied in aerobic brook sediments from 39 drainage areas in Finland. The culturable counts of mycobacteria were related to climatic conditions, characteristics of the drainage area, chemical characteristics of the sediment and water, culturable counts of other heterotrophic bacteria, and microbial respiration rate in the sediment. The counts of mycobacteria varied from 1·1 × 10 2 to 1·5 × 10 4 cfu g −1 dry weight of sediment. They correlated positively with the proportion of the drainage area consisting of peatland, total content of C, content of Pb, microbial respiration rate in the sediment, and chemical oxygen demand of the water. The correlations of the mycobacterial counts with pH of sediment and alkalinity of water were negative. The results of the present sediment study and of the forest soil study published earlier strongly suggest that an increase in acidity increases the counts of mycobacteria and decreases the counts and activity of other heterotrophic bacteria. Mycobacterial counts were more than 100 times higher (per dry weight) in forest soils with pH 3·5-4·3 than in sediments with pH 4·5-6·3.

No abstract

No abstract

To assess the effect of peatland type and of forest‐drainage performed 30 yr earlier on the occurrence of mycobacteria in runoff‐waters, the counts of culturable mycobacteria were followed during a snow‐free season. Runoff‐waters were from a natural and a drained peatland and each had a different nutrient status. Samples were collected in May, June, August, and October of 1992. Mycobacteria were isolated from all waters. The highest culturable counts were detected in August (up to 7.3 × 103 CFU/L). The runoff‐waters from the two natural peatlands had similar median counts, whereas lowering of the water table by drainage slightly increased the mycobacterial counts in most cases. Changes in vegetation, such as a decrease in the coverage of Sphagnum species, or soil characteristics following drainage had little effect on the occurrence of mycobacteria in the runoff‐waters, even though Sphagnum vegetation has been regarded as important for the growth of these bacteria. The counts of mycobacteria in the runoff‐waters correlated with precipitation but not with air temperature. This indicates that the mycobacterial growth took place mainly in vegetation and soil, not in the runoff‐waters. When total runoff during May to October was taken into account, the leaching rates of mycobacteria from all catchments were about 4 to 5 × 1011 CPU km−2. Thus drainage had a negligible effect on the leaching of mycobacteria from peatlands.

Taxonomic studies were performed on a phenotypically homogeneous group of 13 mycobacteria isolated from clinical, veterinary and stream-water samples. The methods applied included chromatographic analyses of bacterial lipids, biochemical tests and sequencing of the 16S rDNA and the internal transcribed spacer 1 (ITS1) region. Positive results in urease, Tween 80 hydrolysis and pyrazinamidase tests and a negative result in a semi-quantitative catalase test, combined with the ability to grow at 42 degrees C, distinguished this group among the yellow-pigmented, slowly growing mycobacteria. Unique fatty acid and mycolic acid profiles in chromatographic analyses and the results of gene sequencing indicated that the novel isolates represent a previously undescribed species, for which the name Mycobacterium palustre sp. nov. is proposed. The fatty acid profile obtained by GLC was characterized by the presence of several methyl-branched fatty acid markers. The most prominent markers were 2-methyleicosanoic, tetracosanoic and hexacosanoic acids. According to 16S rDNA sequencing, M. palustre is phylogenetically closest to Mycobacterium kubicae, a recently described species. M. palustre gives a false-positive result in a hybridization test with the AccuProbe Mycobacterium avium complex. One of the strains was isolated from a lymph-node biopsy from a child with cervical lymphadenitis. Thus, M. palustre should be listed among potential inducers of paediatric lymphadenitis. The veterinary isolates originated from the lymph nodes of slaughter pigs. The majority of the strains were recovered from natural waters, which highlights the role of the environment as a source of potentially pathogenic mycobacteria. The type strain of M. palustre is strain E846T (= DSM 44572T = ATCC BAA-377T).