Studies on the identity and activity of saprophytic bacteria on stored barley
Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Microbiology
Degree name
Doctor of Philosophy
Publisher
University of Canterbury. Microbiology
Journal Title
Journal ISSN
Volume Title
Language
Date
1970
Authors
Allen, J. D.
Abstract
- The epiphytic micro flora of barley seed was investigated to determine the kinds of bacteria present, and the possibility of their growth at low levels of water activity.
- Identification of the bacteria was based on similarity indices computed for each isolate.
- On developing grain in the field, yeasts (Rhodotorula) were the first microorganisms to colonize the seed in large numbers. Subsequent growth of bacteria reached a maximum one week before harvest, and then declined somewhat. At the peak of microbial development, it was estimated that 15-20% of the seed surface was occupied by microorganisms.
- A survey of sack-stored barley showed that the largest single group of bacteria on the grain was composed of Erwinia herbicola. This accounted for 45% of the total isolates. Several other groups formed a heterogeneous collection of gram-variable or gram-positive coryneform bacteria, which together made up a further 38% of the total. Pseudomonades, flavobacteria and cocci were of lesser importance.
- On stored seed attacked by granary weevils (Sitophilus granarius) there was a decrease in the numbers of bacteria found and, on seed which had previously been sterilized, a corresponding increase in numbers of Aspergillus glaucus. Aspergilli were not found on un-sterilized seed but this was not considered to be the result of antagonism by the saprophytic microflora.
- Bacteria were shown to multiply on seed kept at atmospheric humilities of 75%, 95% and 100% R.H. Although the rate of increase was inversely proportional to the humidity, the maximum population attained was the same in each case, and once attained it was immediately followed by a drop in numbers. These results were interpreted as indicating that in a physiological sense, xerophytic bacteria do occur on barley, but that this is of no ecological significance because in-the absence of liquid water the growing colony is soon poisoned by its own metabolic wastes.
Description
Citation
Keywords
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
Rights
Copyright J. D. Allen