MICROBIOLOGY
ECOLOGY
FEMS Microbio!cgj Ecology 23 (1997) 325-332
Mycobacteria in boreal coniferous forest soils
Eila
I(. Iivanainen
"I*,
Pertti J. PV2artikaiiien", Pvlai-ja Liisa RGsgiien ",
Marja-Leena Katila
"
" Luhoratorj cf Envzronmental Microbiology, National Public Health Institut(,, P 0. Box Y j , FIIV-70701 Kuopio, Finland
" Geochcm~culDepartment, Geological Survey of Finland, P. 0. Box 1237, FIN-70211 Kuopio, Finland
Department of Clinical ~Wicrobic)logy,Kuopio Univer.~ityHospitui, P.O. Box 1777, FIN-70211 Kuopio, Finiand
Received 25 November 1996; revised 21 May 1997; accepted 22 May 1907
Abstract
The occurrence of mycobacteria was studied in organic horizons of coniferous forest soils in Finland and related to
environmental variables, i.e. plate counts of other heterotrophic bacteria, microbial respiration rate, chemical soil
characteristics. vegetational characteristics and climatic conditions in the stbidy period. Mycobacteria were isolated from 111
samples (n=47), with plate counts varying from 4.5X lo4 to 1.2X 10"ru
g-' dry soil. The plate counts of mycobacteria
correlated positively with those of other heterotrophic bacteria, microbial respiration rate and the contents of Ca and Mn. In
factor analysis, the viable cnl~ntsof mycobacteria and other heterotrophi~bacteria, and respiration rate were grouped in the
same factor emphasizing that mycobacteria and other heterotrophic bacteria had similar associations with environmental
characteristics. The plate counts of mycobacteria and other heterotrophic bacteria and microbial respiration rate were similar
in organic horizons of pine and spruce dominated forests. The large number of mycobacteria in all organic horizons indicates
that boreal coniferous forest soils are important sources for these bacteria.
Kej~word?: htypiila! mycobzcteriurr; Heterolrophic basterim; Coniferous fbrest; Vegetatior;; Soil
1. Introduction
The increasing importance of atypical mycobacteria as human pathogens [l-31 and the lack of evidence for human-to-human transmission of infections caused by these bacteria [3] have stimulated
the research on their environmental occurrence and
ecology. Several studies on natural waters, water distribution systems, and soils have shown the ubiquitous presence of these heterotrophs in the environ-
* Corresponding author. Tel.: +358 (17) 201375; Fax:
+358 (17) 201 155; E-mail: [email protected]
ment [4-61. Some studies on the ecology of
mycobacteria have suggested that low pH and high
content of organic matter favor the occurrence of
mycobacteria in the environment [7-101. In general,
however, there is little knowledge on factors affecting
the occurrence of mycobacteria in soils. Coniferous
forests are the most common forest type in boreal
regions. They have a podzolized soil profile with an
acidic organic horizon, which is the most important
layer for microbial growth in these soils [11,12]. The
chemical composition and microbiological characteristics of the organic horizon are highly dependent on
litter production of vegetation. The boreal conifer-
0168-64961971$17 00 % 1997 Federdtlon of European Microbio1og1cal Societies Published by Elsevier Science B V
PIIS01 68-6496(97)00040-8