Dix'oMi'osrnoN oi' coMi'i.iix rhAN'i" AND AMM Ai, i{ lisi I )ri;s 



247 



tliat act iiioiuycc'U's ai't \\v\\ (Iccoiuijosc plant 

 protoiiLS, lilx'ratinij; tlu> nit rof^cii as ammonia. 

 Decomposition of protein fil)ors by aclino- 

 niycctos lias hccn studied by ( Joldsmilli. 'V\\v 

 enzymatic meciiaiiisms in\()l\-ed in protein 

 decomposition l\v actinom_\cctes are dis- 

 cussetl in Chapter 1 1. 



Li<l)iiii I)( composition 



In conn(H'ti()n with tht> decomposition of 

 phmt materials in soils and in composts the 

 effect of actinomycetes on the Hgnin is of par- 

 ticuhir interest. It is now well recognized 

 that the hgnins and the proteins contribute 

 greatly to the formation of hiuiius in soils 

 and in composts. As the plant materials are 

 decomposed by fungi and bacteria, there is 

 usually an increase in the concentration of 

 the lignin, since most of these organisms do 

 not attack this complex \'ery readily (Waks- 

 man). This accumulation of the lignin is par- 

 alleled by an increase in ash content and 

 often in the protein content in the case of 

 nitrogen-poor materials, and ))y a decrease 

 in the total dry material. Through their abil- 

 ity to attack the resistant lignins, the actino- 

 mycetes have the capacity to leave an or- 

 ganic residue with a lower lignin content. 



Decompostion of Other Organic Complexes 



Actinomycetes are capable of growing on 

 and decomposing a great variety of other 

 organic materials. These include paraffins 

 (Baldacci, 1947), waxes, rubber, and build- 

 ing materials (McLachlan, 1946). The ability 

 to attack paraffins is characteristic of certain 

 nocardias, as shown elsewhere in the descrip- 

 tion of the individual species in Chapter 23 

 (Volume II). 



Formation and Decomposition of Hu- 

 mus 



On the basis of the foregoing obser\-ations, 

 the conclusion may easily be reached that 

 actinomycetes take an active part in the for- 

 mation and decomposition of organic mat- 



'I'ami.io 74 

 I iijliicttrc of dried hlood (I per cent} ii fxni tin 

 inuHbers of J'lDuji (uid (ictiiiomifccles in rdrioim 

 soils after 12 daijH (Wuk.sman ami Sturkoy) 



ter or humus in the soil. This comprises both 

 nitrogenous and nonnitrogenous organic sub- 

 stances. Because of their ability to attack 

 native lignin, actinomycetes may even be ex- 

 pected to play a unique role in the forma- 

 tion and transformation of humus materials. 



The role of actinomycetes in the formation 

 of dark colored compounds and the possible 

 bearing of these compounds upon humus for- 

 mation were first pointed out by Beijerinck. 

 He emphasized that the black pigment pro- 

 duced by some of these organisms on protein 

 media may function as an oxidizing agent. 

 On the basis of this, he tried to postulate 

 their significance in natural processes, notably 

 in the humification of soil organic matter. He 

 correlated this with the abundance of actin- 

 omycetes at different soil depths. 



The results of Beijerinck were confirmed 

 and further extended by Fousek, Mimter, 

 Krainsky, and Waksman, and later by von 

 Plotho, Lantsch et al., and Scheffer et al. 

 The ability of various streptomyces to give 

 rise to dark brown substances, comparable 

 to humic acids, was demonstrated recently 

 by Flaig et al. (1952), Kuster (1952), and 

 Beutelspacher (1952). The formation of such 



