ISOLATION, CULTURE, AND DEGRADATIVE BEHAVIOR OF THE LICHEN PARASITE HOBSONIA-SANTESSONII

The fact that lichens are generally well-defended chemically against p athogens suggests that mycoparasites known to attack lichens (parasiti c lichenicolous fungi) have been able to overcome lichen chemical defe nses. Recently, an isolate of the relatively specialized lichen mycopa rasite Hobsonia santessonii was obtained from Peltigera scabrosa colle cted in northern Sweden. In laboratory experiments, the ability of thi s lichen parasite to degrade lichen tissues was compared with that of a related nonlichenicolous species, Hobsonia mirabilis. The lichen pat hogen H. santessonii was able to degrade a variety of lichens, includi ng a Peltigera species; interestingly, the degradation was greater for tissues with lichen compounds present than it was when compounds were removed using acetone. The nonlichenicolous H. mirabilis also exhibit ed degradative ability, in some cases greater than that of H. santesso nii; however, acetone-soluble lichen compounds were far more inhibitor y for H. mirabilis than for H. santessonii. These results indicate a s imilarity in the general types of degradative polysaccharidases produc ed by these apparently related fungi; however the more specialized H. santessonii appears to produce enzymes that are more tolerant of liche n compounds.