Liquid Culture Production Research Articles

Production and localization of restrictocin in Aspergillus restrictus.

The production and secretion of restrictocin (a cytotoxin that cleaves ribosomal RNA) by cultures of the fungus Aspergillus restrictus was investigated. Previous studies have indicated that restrictocin production in liquid culture coincides with the appearance of differentiated cell structures. A study of the correlation between the appearance of differentiated structures and restrictocin production was conducted with A. restrictus grown on agar medium. Restrictocin was found to be associated with the cell mass of the agar-grown culture (in contrast to liquid cultures), and was first observed when aerial hyphae emerged. Restrictocin levels increased until the time of conidiation, after which they fell off sharply. No restrictocin could be found in the agar medium. The presence of restrictocin upon and within various cell structures was determined by immunofluorescent laser microscopy. This study showed that restrictocin became localized to the conidiophores and phialides during the process of conidiation. Prior to this, restrictocin was found within the hyphae in localized concentrations that may correspond to secretory vesicles.

Tn [formula omitted] mutagenesis of chinese Rhizobium fredii for siderophore overproduction

In the midwestem United States, members of USDA Bradyrhizobium japonicum serogroup 135 dominate in alkaline soils for nodulation of soybean [ Glycine max (L.) Merr.], whereas members of USDA serogroup 123 dominate in non-alkaline soils. A possible explanation for the dominance of 135 in alkaline soils is that native 135 strains can produce siderophores that assist in acquiring iron. Our objectives were to test six reference strains (three slow-growing B. japonicum and three fast-growing Rhizobium fredii) for siderophore production and to evaluate mutants of R.fredii (developed by Tn 5 -insertion for overproduction of siderophores) for their competitive abilities in an alkaline soil. B. japonicum reference strains USDA 110, 123 and 135 were tested for siderophore production in liquid culture by using Neilands' CAS Assay Solution. Mutants were developed for siderophore overproduction by introducing transposon Tn 5 (Km r) into a siderophore-producing Chinese R. fredii strain. Two siderophore overproducing mutants that produced mature and pink nodules on soybean in growth pouches were examined for the presence of Tn 5 by Southern hybridization with a Tn 5 probe. The Tn 5 -carrying mutants were further tested in the greenhouse for their competitiveness against native strains present in an alkaline soil of Iowa and for their symbiotic effectivity. Among the three slow-growing bradyrhizobia tested for siderophore production, USDA 135 was the only strain producing siderophore in a liquid medium low in iron. Nodule occupancies in the greenhouse by the two siderophore overproducing mutants of R. fredii were 3 and 4%, compared with 19% for the wild-type strain. Thus, either the wild-type was acquiring all the iron needed for maximum growth and nodulation, or the insertion of Tn 5 and the overproduction of siderophore resulted in less competitive strains.

5023183 Mass production in liquid culture of insect-killing nematodes: Milton J Friedman, Susan E Langston, Soni Pollitt assigned to Biosys Corporation

5023183 Mass production in liquid culture of insect-killing nematodes: Milton J Friedman, Susan E Langston, Soni Pollitt assigned to Biosys Corporation

Development and analysis of pectic screening media for use in the detection of pectinase mutants

Two solid pectic media were devised for mutually exclusive detection of extracellular polygalacturonase and pectin lyase produced by fungi including the vascular parasite of tomato Verticillium albo-atrum. These media allowed detection of pectinase-defective mutants. Polygalacturonase detection medium contains non-methylated polygalacturonan (sodium polypectate) is buffered at pH 5.0 (Na citrate, 0.05 M) and is calcium-free. In contrast pectin lyase medium contains polymethylgalacturonan (pectin), is buffered at pH 8.0 (HEPES, 0.05 M) and contains calciumrich agar. When glucose was added to the media for selection of catabolite-resistant mutants, enzyme synthesis was still evident, whereas in comparable conditions in liquid culture production was almost completely repressed. This apparent discrepancy is discussed in terms of the influence of basal synthesis, colony biomass and accumulation of oligouronides which repress induced synthesis and activity.

Polygalacturonase production in liquid culture by isolates of Gaeumannomyces graminis and Phialophora-like fungi from cereal roots

Polygalacturonase production in liquid culture by isolates of Gaeumannomyces graminis and Phialophora-like fungi from cereal roots