Actinomycetes are widespread in the environment and are mainly organot
rophic. Studies of their ecology have been primarily focussed on their
detection and isolation, with comparatively little attention to the c
ontrol mechanisms that determine their occurrence and behaviour in the
ir natural environments. This session provided some diverse examples o
f approaches to this problem. Several actinomycete genera produce moti
le spores. The significance of flagella proteins and factors influenci
ng spore motility and germination are considered. The genus Frankia fo
rms nitrogen-fixing associations with non-leguminous plants. Molecular
techniques have been used to clarify the endophyte-host relationships
. Micromonospora species are common in the environment. The growth and
physiology of a gentamicin-producing strain are described. Thermophil
ic actinomycetes in the genus Thermoactinomyces are common in composts
and other self-heating environments. Novel isolates from acid soil, w
hich grow and produce enzymes active at high temperatures and in acidi
c conditions, are discussed.