Phenotypic characteristics of 60 strains of Propionibacterium isolated from anaerobic hybrid digesters treating landfill leachate and a baker's yeast factory effluent were analysed using numerical taxonomy. With the use of the SsM similarity coefficient, 92% of the anaerobic digester strains were grouped in eight major clusters. The isolates were identified by relating them to specific type strains and comparison of phenotypic characteristics. These clusters were equated with the 'classical' species P. acidipropionici, P. freudenreichii, P. jensenii and P. thoenii using the current classification system. Some of the digester isolates were identified to specifies level using the current identification system, but based on overall similarity they were clustered among members of another species. Furthermore, the data indicated that there was low similarity between the digester isolates and the type strains of P. jensenii and P. thoeni. A hypothesis is presented as to the role of these propionic acid-producing bacteria during the granulation process found in anaerobic digesters.
T.J. BRITZ AND K‐H.J. RIEDEL. 1991. Phenotypic results from 81 tests conducted on 73 propionibacteria, including five type strains, 22 reference strains, unidentified propionibacteria and strains isolated from dairy sources, were analysed by numerical taxonomy. Characters giving uniform results were excluded. With the simple matching coefficient and the single linkage cluster analysis, 61 cultures were recovered in five major clusters. Final linkage of all the Propionibacterium cultures examined was at the 77% S‐level. The results clearly showed that it was possible to distinguish between the ‘classical’ and ‘cutaneous’Propionibacterium spp., corresponding with the type habitat of each group. The major ‘classical’ clusters were equated with the P. freudenreichii, P. thoenii, P. jensenii and P. acidipropionici species, while the only major ‘cutaneous’ cluster was equated with the P. acnes species. The major clusters were identified by relating them to specific type strains and by comparing phenotypic characteristics. The differentiating characteristics of each cluster were determined. The largest cluster, representing 37% of the strains, was equated with P. jensenii but contained cultures that produced an atypical brown/red pigment. These strains, although positively identified as P. jensenii, could also be identified as the ‘old’‘P. rubrum’ species. Thus if pigmentation is used as differential characteristic two distinct groups of propionibacteria could be identified within the P. jensenii species.
Research on the distribution of oxylipins (3-hydroxy fatty acids) in flocculant strains of the yeast Saccharomyces cerevisiae led to the uncovering of a novel 'ghosting' phenomenon observed during assumed lectin-mediated aggregation. We found that intracellular oxylipin-containing osmiophilic layers migrate through yeast cell walls in a 'ghostlike' fashion without visually affecting the cell wall structure or the layers. This migration resulted in the binding of these layers to cell walls of adjacent cells. Consequently, 'ghosting' seems a prerequisite for flocculation to occur. However, 'ghosting' alone may not be sufficient to ensure flocculation.
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