Author: Fransiscu Lamahewage Thisal Dewin Jayawardena
Jayawardena, Fransiscu Lamahewage Thisal Dewin, 2024 MICROBIAL ABUNDANCE ACROSS GOYDER'S LINE: A COMPARATIVE SOIL BACTERIAL ABUNDANCE VARIATION STUDY TO MITIGATE DROUGHT CONDITIONS, Flinders University, College of Medicine and Public Health
Terms of Use: This electronic version is (or will be) made publicly available by Flinders University in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. You may use this material for uses permitted under the Copyright Act 1968. If you are the owner of any included third party copyright material and/or you believe that any material has been made available without permission of the copyright owner please contact copyright@flinders.edu.au with the details.
The Goyder's Line is a significant demarcation line in South Australia. This surveyed line is a vital and historic terrestrial marker separating regions with an average annual rainfall of 250 mm. There is a clear research gap presented with a lack of knowledge on microbial population abundance and the environmental factors such as rainfall which contribute to changes in microbial abundances within the region. This study observed bacterial abundances in ten sites north and south of the Goyder’s line. The abundance of bacterial populations was calculated using flow cytometric analysis, and environmental factors that influence the abundance of bacteria, such as pH, were also measured. The abundance values and other factors were visualized using Pearson's Correlation and Independent Samples T-test. Mean bacterial abundance was significant in the south (p=0.040), with a greater bacterial abundance of M= 6.0x 106 ± 7.5 x105 cells ml-1 compared to the north which was M= 3.7 x 106 ± 4.9 x105 cells ml-1. Although not significant (p=0.452), The ridge had a mean bacterial abundance M = 3.6x106 ± 3.9x 105 cells ml-1 compared to the furrows, which were (M = 4.4x106 ± 8.6x105cells ml-1. Virus-like particle abundances were not measured as it was harder to differentiate them from the noise controls. The Pearson correlation of pH to the abundance of bacteria was (r) = - 0.365 and a significance value of (p= 0.299) which made it statistically insignificant, Isolated observations indicated that in some samples lower bacterial abundance was present in higher pH values as well as agricultural practices such as animal grazing between crop rotations also promoted bacterial abundance Because these observations could not be statistically proven further research should be done to obtain a clear idea on this matter. Furthermore, several environmental conditions such as salinity, availability of Phosphorus, Potassium, Nitrogen, and soil organic carbon were identified that influenced the abundance of bacteria that were not tested in this study. The main conclusion of the study is that although rainfall had a significant influence on soil microbial abundance furrows which were assumed to have higher levels moisture of did not have a significant influence. The future direction of this study is to identify the taxa in the soils that contributed to the abundance and identify bacteria that contain drought-resistant genes or produce substances such as extracellular polysaccharides (EPS).
Keywords: Goyders line, Rainfall, Flow cytometry, pH
Subject: Medical Biotechnology thesis
Thesis type: Masters
Completed: 2024
School: College of Medicine and Public Health
Supervisor: Prof. Jim Michell