9,535 research outputs found
Characterisation of dairy strains of Geobacillus stearothermophilus and a genomics insight into its growth and survival during dairy manufacture : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Microbiology at Massey University, Palmerston North, New Zealand
The thermophilic bacilli, such as G. stearothermophilus, are an important group of contaminants in the dairy industry. Although these bacilli are generally not pathogenic, their presence in dairy products is an indicator of poor hygiene and high numbers are unacceptable to customers. In addition, their growth may result in milk product defects caused by the production of acids or enzymes, potentially leding to off-flavours. These bacteria are able to grow in sections of dairy manufacturing plants where temperatures reach 40 â 65 °C. Furthermore, because they are spore formers, they are difficult to eliminate. In addition, they exhibit a fast growth rate and tend to readily form biofilms. Many strategies have been tested to prevent the formation of thermophilic bacilli biofilms in dairy manufacture, but with limited success. This is, in part, because little is known about the diversity of strains found in dairy manufacture, the structure of thermophilic bacilli biofilms and how these bacteria have adapted to grow in a dairy environment.
In Chapters 2 and 3, phenotypic approaches were taken to understand the diversity of strains within a manufacturing plant. Specifically in Chapter 2, strains of the most dominant thermphilic bacilli, G. stearothermophilus, were isolated from the surface of various locations within the evaporator section and ten strains were evaluated for different phenotypic characteristics. Biochemical profiling, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and fatty profiling demonstrated that the population was diverse. In Chapter 3, it was shown that the same ten strains varied in their ability to form biofilms and produce spores. Three strains of G. stearothermophilus, A1, P3 and D1, were selected for further analysis. SEM demonstrated that there were differences in biofilm morphologies between the three strains, particularly D1 versus the other two strains, A1 and P3.
In Chapters 4, 5 and 6 a comparative genomics approach was taken to determine how these bacteria are able to grow and survive within a dairy manufacturing environment, as well as how they differ from other strains of Geobacillus. In Chapter 4 draft genome sequences were generated for three strains of G.stearothermophilus. Identification of a putative lactose operon in the three dairy strains provided evidence of dairy adaptation. In Chapter 5 a phylogenomics approach was taken to resolve relationships within the Geobacillus genus and to identify differences within the G. stearothermophilus group itself. Finally in Chapter 6 comparison with the model organism B. subtilis, gave a genomics insight into the potential mechanisms of sporulation for Geobacillus spp
Caldolysin, a highly active protease from an extremely Thermophilic Bacterium
Proteases comprise a significant proportion of those proteins which have been subject to detailed characterisation (amino acid sequence and high resolution crystallographic analysis). The extent of research interest in proteolytic enzymes reflects both their historical status, and the practical advantages of proteases as research subjects (available in quantity, extracellular etc.) widely occurring
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Protein evolution speed depends on its stability and abundance and on chaperone concentrations.
Proteins evolve at different rates. What drives the speed of protein sequence changes? Two main factors are a protein's folding stability and aggregation propensity. By combining the hydrophobic-polar (HP) model with the Zwanzig-Szabo-Bagchi rate theory, we find that: (i) Adaptation is strongly accelerated by selection pressure, explaining the broad variation from days to thousands of years over which organisms adapt to new environments. (ii) The proteins that adapt fastest are those that are not very stably folded, because their fitness landscapes are steepest. And because heating destabilizes folded proteins, we predict that cells should adapt faster when put into warmer rather than cooler environments. (iii) Increasing protein abundance slows down evolution (the substitution rate of the sequence) because a typical protein is not perfectly fit, so increasing its number of copies reduces the cell's fitness. (iv) However, chaperones can mitigate this abundance effect and accelerate evolution (also called evolutionary capacitance) by effectively enhancing protein stability. This model explains key observations about protein evolution rates
The industrial potential of enzymes from extremely thermophilic bacteria
The thermal regions of the central North Island of New Zealand are some of the most extensive in the world. In addition, they are readily accessible and contain a diversity of ecological habitats, including a large number at 100°C. These areas are regarded as an important tourist attraction, and as a source of geothermal power, It is now clear that they also contain an important and unique genetic resource
Thermophile
Master of Fine Arts (MFA)University of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/134027/1/JohnVerney2016MFA-thesis.pd
Proton and cadmium adsorption by the archaeon Thermococcus zilligii: Generalising the contrast between thermophiles and mesophiles as sorbents
Adsorption by microorganisms can play a significant role in the fate and transport of metals in natural systems. Surface complexation models (SCMs) have been applied extensively to describe metal adsorption by mesophilic bacteria, and several recent studies have extended this framework to thermophilic bacteria. We conduct acid-base titrations and batch experiments to characterise proton and Cd adsorption onto the thermophilic archaeon Thermococcus zilligii. The experimental data and the derived SCMs indicate that the archaeon displays significantly lower overall sorption site density compared to previously studied thermophilic bacteria such Anoxybacillus flavithermus, Geobacillus stearothermophilus, G. thermocatenulatus, and Thermus thermophilus. The thermophilic bacteria and archaea display lower sorption site densities than the mesophilic microorganisms that have been studied to date, which points to a general pattern of total concentration of cell wall adsorption sites per unit biomass being inversely correlated to growth temperature
Biased amino acid composition in warm-blooded animals
Among eubacteria and archeabacteria, amino acid composition is correlated with habitat temperatures. In particular, species living at high temperatures have proteins enriched in the amino acids E-R-K and depleted in D-N-Q-T-S-H-A. Here, we show that this bias is a proteome-wide effect in prokaryotes, and that the same trend is observed in fully sequenced mammals and chicken compared to cold-blooded vertebrates (Reptilia, Amphibia and fish). Thus, warm-blooded vertebrates likely experienced genome-wide weak positive selection on amino acid composition to increase protein thermostability
Mollusca in marginal marine and inland saline aquatic ecosystems â examples of Cretaceous to extant evolutionary dynamics
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Systematic analysis of the Hippo pathway organization and oncogenic alteration in evolution.
The Hippo pathway is a central regulator of organ size and a key tumor suppressor via coordinating cell proliferation and death. Initially discovered in Drosophila, the Hippo pathway has been implicated as an evolutionarily conserved pathway in mammals; however, how this pathway was evolved to be functional from its origin is still largely unknown. In this study, we traced the Hippo pathway in premetazoan species, characterized the intrinsic functions of its ancestor components, and unveiled the evolutionary history of this key signaling pathway from its unicellular origin. In addition, we elucidated the paralogous gene history for the mammalian Hippo pathway components and characterized their cancer-derived somatic mutations from an evolutionary perspective. Taken together, our findings not only traced the conserved function of the Hippo pathway to its unicellular ancestor components, but also provided novel evolutionary insights into the Hippo pathway organization and oncogenic alteration
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