The unusual sclerotium of Rhizopogon roseolus reported from pure cultures

During the assessment of mycelial cords of Rhizopogon roseolus on poor nutrient of Modified Melin-Norkrans (MMN) medium, we found some sclerotia produced on the surface of extraradical mycelia. The sclerotia were 0.27 mm in average of diameter and produced after 2 months of incubation. The current knowledge defined the sclerotium as mass of hyphae and normally having no spores in or on it. However, we found and suspected the small structures like spores (1-1.5 um) inside the sclerotium. These structures were ellipsoid, hyaline, with the smooth surface. We then incubated the sclerotium and these small structures on TM7 detecting medium whether they can produced the secondary mycelia of R. Roseolus, but no germination was observed. Interestingly, the bacterial colonies which connected to hyphae of sclerotium were appeared. The colonies were transferred to Luria agar (LA) medium. The morphological observation of bacterial cells from TM7 and LA confirmed that they were the same as small structures inside the sclerotium. This is the first report on production of unusual sclerotium of R. roseolus in pure cultures. Further study is required to reveal the role of bacteria on production of sclerotium of R. Roseolus.

Colicinogeny among Escherichia coli Serotypes, Including O157:H7, Representing Four Closely Related Diarrheagenic Clones

Twenty-seven diarrheagenic Escherichia coli (DEC) strains from five closely related, genetically distinct clones (DEC 3, 4, 8, 9, and 10), representing serotypes commonly associated with Shiga-like toxin production, i.e., 015:H−, 026:(H11, H−), 0111:(H8, H11, H−), and O157:H7, were evaluated for colicinogeny on Luria agar or Luria agar containing 0.25 μg/ml mitomycin C to induce colicin production. Ten (37%) of the DEC strains tested were colicinogenic. One of 11 serotype O157:H7 strains, DEC strain 4E, produced a colicin identified as Col D. DEC strains 8B, 9D, and 10B produced Col E1, whereas DEC strain 10A produced Col E2. DEC strains 8A, 8E, 10C, 10E, and 10F produced “untypable” colicins that killed almost all Pugsley Colicin Reference Set strains and the other DEC strains tested. To aid with further characterization of the colicins, plasmids extracted from each colicin-producing (Col+) DEC strain were used to transform E. coli strain DH5α. All Col+ DH5α transformants contained one plasmid ranging in size from 1.3 to 10 kb. Some transformants were stable colicin producers whereas others were unstable. The inhibitory activity and colicin sensitivity and insensitivity profiles of the Col+ transformants were similar to those of the corresponding Col+ donor DEC strains. It appears that the untypable colicins are novel and, thus, warrant further study. Colicin production by some of the DEC strains evaluated partly explains why they were insensitive to standard colicins in a previous study.