280 NITROGEN NUTRITION AND METABOLISM 



shake culture (5, 6, 7). The ergot alkaloids, whether produced by 

 the fungus or supplied exogenously, disappear in time from a culture 

 (4, 363). 



9. MISCELLANEOUS NITROGEN COMPOUNDS 



Although the antibiotics of actinomycetes form a large share of the 

 known nitrogenous metabolites, a number of fungal products are also 

 known. Table 2 lists some representative compounds in a classifica- 

 tion based on chemical similarity. Almost nothing is known of bio- 

 chemical relationships. 



Group I of Table 2 includes compounds more or less similar to 

 amino acids. Azaserine is of some general interest by reason of its 

 apparently specific blocking of a single step in the biogenesis of purine 

 nucleotides (49, 543). Other serine derivatives include the anti- 

 biotic cycloserine and the non-antibiotic O-carbamyl-D-serine (223), 

 both actinomycete products. Mycelianamide, produced by Penicillium 

 griseofulvum, is structurally related, as an acylhydroxylamine, to cy- 

 closerine (57). 



The structure of the related antibiotics thiolutin and aureothricin 

 has been determined (97), and their resemblance to cystine has been 

 noted (14). 



Compounds more closely and obviously related to the amino acids 

 include fumaryl-DL-alanine of Penicillium resticulosum (58), an uni- 

 dentified ester of glutamine in Lepiota naucina (502), and the lichen 

 product picroroccelin, a diketopiperazine (27). 



The organic nitro group occurs only rarely in biological material; 

 chloramphenicol (Chapter 6) is one example, /3-nitropropionic acid 

 another (Table 2). An antibiotic of Streptomyces thiolutens has the 

 nitro group (238). Neurospora crassa forms an inducible enzyme 

 acting on /?-nitropropionic acid and related compounds (328). 



Indigo is shown in Table 2 as a representative of Group III, com- 

 pounds related to indole. There is good evidence that indole is the 

 starting point for indigo formation by both soil bacteria (213) and in 

 the mammalian gut (121); indole in turn, we may assume, arises from 

 tryptophan. 



The indole nucleus is found also in lysergic acid (p. 279), and in 

 echinulin, a product of Aspergillus glaucus (425). Gliotoxin, pro- 

 duced by Aspergillus fumigatus, Penicillium spp., and Trichoderma 

 viride (74), is believed to have a reduced indole nucleus (281). Peni- 

 cillium terlikowski, earlier identified as P. obscurum, forms both glio- 

 toxin and its monoacetate (282). 



Fusaric acid is the sole representative of Group IV, pyridine deriva- 



