Among 327 strains of Actinomycetes isolated in 1958 during the four seasons, 97,85 per cent had proteolytic activity. Most of the strains wete isolated in spring time. About the organic matter no conclusions were reached, because it was mantained constant with a average value of 4.099. So the different number of the strains was a consequence of the season. We can conclude that the Latosol red-yellow soil, from where these microorganisms were isolated, has a strong proteolytic capacity, since this reaction is very strong in a maximum limit of sixteen days during the spring season. Consequently, this soil has one of the most importante caracteristics of fertility. The role of the Actinomycetes in the soil is so important of the soil microflora.

Electron microscopical studies were made of changes in cotton fiber microstructure on samples from cultures of the bacterium Cellvibrio fulvus and the fungus Myrothecium verrucaria. Bacterial colonies, growing in the folds of the primary wall, caused diagonal or longitudinal splitting of the fiber surface. Degradation by the fungus was charac terized by transverse cracks in the fiber wall. Other changes in fiber microstructure during microbial growth were similar for both organisms. In areas of intense attack, surface replicas showed single fibrils detached from the underlying structure; on mer cerized fibers, hydrocellulose-like particles on the surface at times obscured the surface structure. Fragmentation patterns indicated a continued breaking down of the fibrillar structure into small fragments and particles. The final degradation products, seen in electron micrographs, resembled particles produced by a limited, heterogeneous acid hydrolysis, but positive identification with hydrocellulose particles has not been made. Cottons modified to produce a more expanded microstructure with higher amorphous cellulose content showed large decreases in resistance to microbial attack. Attack by growing microorganisms was more intense and rapid than degradation by growth filtrates obtained from cultures of cellulolytic fungi, but the mode of degradation was similar.

Incubation studies of factors influencing nitrite oxidation in four California soils were conducted at two temperatures—45° and 75° F. In acid soils nitrite transformations were found to be highly sensitive to nitrite concentration in the soil and were inhibited by very low levels. Nitrite had less effect on the second step of nitrification in alkaline soils. Nitrite oxidizers were shown to be very sensitive to low temperature soil conditions. Although nitrite disappeared rapidly following addition to acid soils, little nitrate was produced during the incubation period. Much of the nitrite-nitrogen was lost from the system. Experiments using acid soils which had been sterilized showed similar losses in added nitrite-nitrogen and lead to the conclusion that these losses result from nonbiological processes. Studies to determine the nature of these losses suggest nitrogen gas as the principal product. Investigations of respiration rates of the soil population where various concentrations of nitrite were added reveal that nitrites inhibit the respiratory activity of the soil microorganisms as a whole and not merely the nitrifying group. Very low concentrations were inhibitory in acid soils; however, in a calcareous soil more than a hundred-fold increase in nitrite concentration was required to achieve the same magnitude of respiratory inhibition.

In papers recently published, Pereira Jr. (9, 10) claimed that coffee fruits have enzimes capable of breaking down the insoluble pectic substance which involves their seeds. This conclusion was drawn from an experiment where freshly pulped coffee fruits were placed in a calcium hydroxide solution containing 0.4% of NaCl as an enzime activator. After this treatment the seeds which were very slimy became apparently clean and could be handled easily. In this paper it is shown that the pectic substance is not eliminated by such a treatment but that it merely becomes herdened by the action of the calcium hydroxide. When seeds so treated were washed and left in water the pectic substance involving the seeds became turgid again giving the seeds the same slimy feeling to the touch that was noticeable prior to the treatment. This process is enhanced by the use of acidulated water after the washing. These results support the conclusions of previous papers (3, 4) showing that the elimination of the pectic substances in pulped coffee berries is due to microorganisms. | Em trabalhos recentemente publicados. Pereira (9, 10) conclui que os frutos de café possuem enzimas capazes de eliminar a substância péctica que envolve as sementes, quando após o despolpomento são eles colocados em água de cal contendo 0,4% de cloreto de sódio. No presente trabalho mostra-se que aquela substância péctica não é eliminada pelo tratamento descrito, mas apenas torna-se endurecida pela ação do cálcio. Quando sementes tratadas da maneira indicada foram lavadas e colocadas em água pura ou levemente acidulada, a substância péctica se reintumesceu e as sementes tornaram-se novamente lisas ao tato e envolvidas pela camada translúcida de substância péctica. Esta conclusão confirma os trabalhos anteriormente publicados (3, 4), que mostraram ser a eliminação da substância péctica, que envolve as sementes de café despolpado, devida a mícrorganismos.