Lytic strains

Table 2. Lytic effects of platinum compounds on E.coli Tau strain (3)...

An antibiotic inhibition zone often appears around Trichoderma spp. interacting with other fungi. The genus contains many species which produce secondary metabolites. Claydon et al. (23) have identified an antibiotic from T. harzianum as a volatile, 6-n-pentyl-2H-pyran-2-one this was recently shown to be an active antibiotic from T. koningii (24). The volatile appeared to be the factor responsible for the coconut smell of some biocontrol-effective strains of T. harzianum (25). However, in a Petri-plate assay, it can be difficult to be certain that antibiosis is involved. As well as competitive growth, lytic enzymes could also contribute to the action and Trichoderma has been shown to produce / -l,3-glucanase and chitinase (26-29). 

Translation of these results into compound I leads to structure X. Unraveling of the strained zwitterion XI derived from this would yield keto aldehyde XII, a structure that plays a central role in the various possible reaction mechanisms that branch off from the starting material I. Furthermore, under photo-lytic conditions, some alkenes react with carbonyl compounds to form four-membered cyclic ethers, namely, oxetanes, by way of a [2-1-2] cycloaddition reaction known as the Patemo-Buchi process. Such a reaction would be all that is necessary to convert XII into the bicyclic cyclopropanone XIII required for the Favorskii-type rearrangement (see Scheme 42.3). Splitting by methanol attack would directly yield compound II. 

Certain strains of bacteria are resistant to the lytic properties of penicillins but remain. su.sccptible to their growth-inhibiting effects. Thus, the action of the antibiotic has been converted from bactericidal to bacteriostatic. This mechanism of resistance is termed tolerance and apparently results from impaired autolysin activity in the bacterium. 

If a particular yeast strain is chosen for the production of single cell protein, it is desirable to grow the chosen microbe on this same yeast to induce lytic enzyme production. The rationale for this is the considerable variation in cell wall composition between yeast species, and the most effective lytic enzyme complex is obtained by using the same strain as enzyme inducer. 

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