24 



THE ACTINOMYCETES, Vol. II 



Figure 8. JV. paraffinae, showing a section of a 

 colony covered with mature aerial mycelium (Re- 

 produced from: Hirsch, P. and Engel, H. Ber. 

 Deut. Botan. Ges. 69: 454, 1956). 



Figure 9. Nocardia, strain 70, showing the de- 

 velopment of the aerial mycelium on mineral agar 

 (Reproduced from: Hirsch, P. and Engel, H. Ber. 

 Deut. Botan. Ges. 69: 454, 1956). 



ignated as N. erythropolis. Microbacterium 

 mesentericum Orla-Jensen was renamed N. 

 mesentericus. 



Jensen divided the genus Nocardia into 

 two distinct groups: 



I. Nonproteolytic organisms with strongly 

 refractive cells showing a partial acid- 

 fastness in milk and sometimes in other 

 media; capable of decomposing paraffin. 

 Some species of this group form a transi- 

 tion to the genus Mycobacterium. 

 II. Mostly proteolytic forms with weakly 

 refractive, nonacid-fast cells. This group 

 forms a close transition to the forms now 

 included in the genus Streptomyces. 

 A further separation of the genus was 

 based upon the structure of the aerial myce- 

 lium. 



A. Unstable mycelium (a-form), with 

 short mycelium (if formed at all), 

 bacterial (diffuse) growth in liquid 

 media, bacteria-like colony. 



B. Stable mycelium (/3-form), producing 

 long hyphae, colony growth in liquid 

 media, and Streptomyces-like type of 

 colony. 



Umbreit (1939) modified the system of 

 Jensen as follows: 

 I. Partially acid-fast, nonproteolytic, non- 

 diastatic ; constantly utilize paraffin. 



1. a-Mycelium type: N. opaca* N. eryth- 

 ropolis. 



2. /3-Mycelium type: 



a. Iled-colored : N. polychromogena 

 N. asteroides. 



b. Yellow-colored: N . paraffinae. 



II. Nonacid-fast forms, constantly diastatic 



1. a-Mycelium type: 



a. Nonproteolytic: N. mesenterica. 



b. Proteolytic: N. actinomorpha. 



2. 0-Mycelium type: 



a. Yellow-colored: N. flavescens. 



b. Red to orange: N. maculata. 

 Krassilnikov (1938) divided the genus 



Nocardia* into two groups: 

 I. Well developed aerial mycelium, with 

 substrate mycelium seldom producing 

 cross walls. The hyphae break up into 

 long, thread-like rods. Branches of the 

 aerial mycelium produce segmentation 

 spores and oidiospores; the latter are cyl- 

 indrical with sharp ends. No spirals or 

 fruiting branches. This is the same as 

 group /3 of Jensen. 



II. Typical nocardial forms. Mycelium de- 

 velops only at early stages of growth, 

 then breaks up into rod-shaped and 

 coccoid bodies. Smooth and rough col- 

 onies, dough-like consistency, similar to 

 bacterial colonies. Aerial mycelium not 

 formed or only around colonies. 



* Generic name Proaclinomyces used. 



