Papers by Elizabeth Watkin
Effects of external NaCI, and of changes in turgor pressure and volume, on K+ concentrations in Chlorella emersonii
Plant, Cell and Environment, 1983
ABSTRACT Soluble potassium concentrations were determined for the slightly vacuolated, unicellula... more ABSTRACT Soluble potassium concentrations were determined for the slightly vacuolated, unicellular, walled alga Chlorella emersonii. Sap of cells grown in 1 mol m−3 NaCI contained 140 mol m−3 K+ and sap of cells grown in 125, 200, and 335 mol m−3 NaCI contained 160-180 mol m−3 K +.The possible regulation of K + concentrations by a system of lurgor and volume maintenance was investigated by supplying 3-0-methylglucose. This solute accumulates to 85-230 mol m−3 in C. emersonii, but is not metabolized. Accumulation of 3-0-methylglucose increased the volume of cells grown at both low and high NaCI by about 10%. Furthermore, accumulation of 3-0-methylglucose also increased turgor pressures of cells grown in 1 and 125 mol m−3 NaCI by 0.3 and 0.2 MPa, respectively. (Similar measurements were not attempted for cells grown in 200 and 335 mol m−3 NaCI, because of the insensitivity of available methods to measure turgor pressure of cells exposed to high external osmotic pressures.)At all NaCI concentrations, the K + concentrations of cells which had accumulated 3-0-methylglucose were only 10-20 mol m−3 lower than K+ in cells which had not been supplied with 3-0-methylglucose. In contrast, accumulation of 3-0-methylglucose greatly decreased concentrations of the endogenous osmotic solutes, proline and sucrose, which accumulated in cells grown in 125 mol m−3 and higher NaCI concentrations.It is concluded that K+ concentrations in Chlorella emersonii are not controlled by a system of turgor and volume maintenance.
Stagnant nutrient solution containing 0n1 % agar and with an extremely low oxygen level (' stagna... more Stagnant nutrient solution containing 0n1 % agar and with an extremely low oxygen level (' stagnant agar solution ') was used to simulate the gaseous composition and slow gas diffusion of waterlogged soils. Comparisons were made between the growth of two wheat cultivars (Triticum aesti um, cvs. Gamenya and Kite) and one triticale cultivar (Triticosecale, cv. Muir) grown in stagnant relative to aerated solution. For all genotypes tested, immersion of roots in stagnant agar solution resulted in the death of the entire seminal root system and led to profuse branching of the laterals of the nodal roots. In the stagnant agar solution aerenchyma, as a percentage of the total cross sectional area of nodal roots, was 18 % for Muir, 14 % for Kite and 12 % for Gamenya ; the roots of species with more aerenchyma also attained a longer maximum root length as predicted by the model of Armstrong (in : Woolhouse HW, ed. Ad ances in botanical research, ol. 7. London : Academic Press, 1979). Muir also had a nodal root\shoot fresh weight ratio of 0n5 compared with 0n2-0n3 in Kite and Gamenya. The greater number and length of nodal roots of Muir did not lead to better shoot growth than in the other genotypes ; one possible reason for this lack of improvement is a low efficiency of aerenchymatous roots in wheat.
The Characterization of Salt Tolerance in Biomining Microorganisms and the Search for Novel Salt Tolerant Strains
Advanced Materials Research, 2009
Short term corrosion monitoring of carbon steel by bio-competitive exclusion of thermophilic sulphate reducing bacteria and nitrate reducing bacteria
ABSTRACT Recent interest has centred on the application of nitrate injection to control reservoir... more ABSTRACT Recent interest has centred on the application of nitrate injection to control reservoir souring. In the present study, the impact of nitrate injection on the corrosion of ASTM A572-50 carbon steel was evaluated. The steel samples were exposed to corrosive production water (high chloride and sulphate) for 21 days at 50 °C. Crude oil and NaNO3 were added as bacterial nutrients. Indigenous bacterial isolates were used and four different conditions were evaluated: control cell (no bacteria), nitrate reducing bacteria (NRB) inoculated cell, sulphate reducing bacteria (SRB) inoculated cell and mixed bacteria (NRB + SRB) inoculated cell. Open circuit potential (Ecorr) and Electrochemical impedance spectroscopy (EIS) were employed to monitor the corrosion process throughout the immersion time. It is shown that the corrosion rates in the cells inoculated with bacteria are lower than the control cell. Both NRB and SRB may offer beneficial corrosion protection to the steel. However, the microscopy results show that localized corrosion in the presence of bacteria is inevitable. Additionally, nitrate promotes the growth of NRB and suppresses the growth of SRB; hence H2S production can be eliminated. NRB oxidize the produced sulphide by SRB and maintain Eh in an inhibitory level to SRB.
Soil Biology and Biochemistry, 1997
The effect of acidity on the growth and survival of six strains of Rhizobium leguminosarum bv. tr... more The effect of acidity on the growth and survival of six strains of Rhizobium leguminosarum bv. trifolii (WU95, NA3001, WSM409, TAl, NA3025 and NA3039) was studied. Acid conditions reduced the growth rate of all strains; mean generation times were 50-60% slower at pH 5.0 than at pH 7.0. The critical pH for growth on solid media was in the range of 4.3-4.6. This is consistent with growth of the strains at different pHs in liquid culture, with NA3001 being the only strain to exhibit a normal growth pattern at pH 4.5. The interaction of acidity and calcium on the growth and survival of three of the strains (WU95, WSM409 and TAl) was studied in the presence of high (300~~) and low (20 FM) concentrations of phosphate. A region of "acid-stress" somewhere below pH 5.0 was observed where growth rate slowed rapidly over 0.2-0.3 of a pH unit. The presence of 300 PM phosphate did not affect the critical pH for growth or growth rate within the "acid-stress" zone, but did reduce the mean generation time of all strains studied at pH above the "acid-stress" zone. At pH 7.0, increasing calcium from 300 PM to 3000 pM had little effect on growth rate, but high calcium increased growth rate within the "acid-stress" zone and enabled growth at a lower pH than that observed with the low calcium concentrations. A four-zone model for the response of root nodule bacteria to acidity is proposed. 0 1997
Physiological responses to acid stress of an acid-soil tolerant and an acid-soil sensitive strain of Rhizobium leguminosarum biovar trifolii
Soil Biology and Biochemistry, 2003
Physiological responses to acid stress in two strains of Rhizobium leguminosarum bv trifolii of d... more Physiological responses to acid stress in two strains of Rhizobium leguminosarum bv trifolii of differing acid-soil tolerance were compared. Acidity affected the size and morphology of the acid-tolerant strain, WSM409, but not of the acid-sensitive strain, TA1. Acid grown cells of WSM409 and TA1 had less cell-associated Ca and Mg and more P than cells grown at pH 7.0. Potassium
Soil Biology and Biochemistry, 2000
The acid-soil tolerance of six strains (WU95, NA3001, WSM409, TA1, NA3025 and NA3039) of Rhizobiu... more The acid-soil tolerance of six strains (WU95, NA3001, WSM409, TA1, NA3025 and NA3039) of Rhizobium leguminosarum bv. trifolii was assessed in a three-year cross-row ®eld experiment in an acid sandy soil of pH 4.2. Strains WSM409, NA3039 and WU95 were more acid-soil tolerant than strains NA3025, TA1 and NA3001. Strains WSM409 and NA3039 colonised and persisted in acid-soil to a greater degree than strains TA1 and NA3001. The data from this study clearly identi®ed strain WSM409 as a strain with outstanding potential for improving the production of clovers on acid soils. 7 : S 0 0 3 8 -0 7 1 7 ( 0 0 ) 0 0 0 5 7 -2
Nucleic Aacid Extraction from Biomining Microorganisms
Advanced Materials Research, 2009
Hydrometallurgy, 2011
2011. The recovery of nucleic acid from biomining and acid mine drainage microorganisms. Hydromet... more 2011. The recovery of nucleic acid from biomining and acid mine drainage microorganisms. Hydrometallurgy. 108 (1-2): pp. 87-92. Please cite this article as: Zammit, Carla M., Mutch, Lesley A., Watling, Helen R., Watkin, Elizabeth L.J., The recovery of nucleic acid from biomining and acid mine drainage microorganisms, Hydrometallurgy (2011), Abstract The cornerstone of biological molecular techniques is the extraction of the intra-or extra-cellular component of interest. However, inefficiencies in the extraction method can lead to results that are not representative of the microbial population under investigation. It is particularly difficult to extract clean and pure samples of the cellular component of interest from the microbial inhabitants of low-pH, sulfidic environments, such as those found in biomining or acid mine drainage (AMD).
Corrosion Science, 2013
The effect of oxygen and biofilms on crevice corrosion of UNS S31803 and UNS N08825 in seawater w... more The effect of oxygen and biofilms on crevice corrosion of UNS S31803 and UNS N08825 in seawater was studied. Passivity breakdown occurred through crevice corrosion in UNS N08825 and through transpassive dissolution in UNS S31803 although both alloys displayed crevice corrosion under potentiodynamic conditions. The most severe crevice corrosion occurred in the absence of oxygen and the presence of a biofilm. Microbial adhesion as investigated by fluorescence microscopy occurred mainly outside the crevice and DNA sequencing revealed a shift in biofilm composition as a function of substratum surface and oxygen pressure.
Plant and soil, 2002
Y. Cheng1,3, ELJ Watkin1, GW O'Hara1 & JG Howieson1,2 1Centre for Rhizobium Studies, Murdoch... more Y. Cheng1,3, ELJ Watkin1, GW O'Hara1 & JG Howieson1,2 1Centre for Rhizobium Studies, Murdoch University, South Street, Murdoch, WA 6150, Australia. 2Agriculture Western Australia, Baron-Hay Court, South Perth, WA 6151, Australia. 3Corresponding author
Standards in genomic sciences, Jan 15, 2014
Burkholderia sp. strain WSM2230 is an aerobic, motile, Gram-negative, non-spore-forming acid-tole... more Burkholderia sp. strain WSM2230 is an aerobic, motile, Gram-negative, non-spore-forming acid-tolerant rod isolated from acidic soil collected in 2001 from Karijini National Park, Western Australia, using Kennedia coccinea (Coral Vine) as a host. WSM2230 was initially effective in nitrogen-fixation with K. coccinea, but subsequently lost symbiotic competence. Here we describe the features of Burkholderia sp. strain WSM2230, together with genome sequence information and its annotation. The 6,309,801 bp high-quality-draft genome is arranged into 33 scaffolds of 33 contigs containing 5,590 protein-coding genes and 63 RNA-only encoding genes. The genome sequence of WSM2230 failed to identify nodulation genes and provides an explanation for the observed failure of the laboratory grown strain to nodulate. The genome of this strain is one of 100 sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project.
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Papers by Elizabeth Watkin