title: Enzymic approach to eurythermalism of Alvinella pompejana and its Episymbionts

authors: Lee, Charles Kai-Wu

subjects: biology

abstract: The equilibrium model, which describes the influence of temperature on enzyme activity, has been established as a valid and useful tool for characterizing enzyme eurythermalism and thermophily. By introducing Keq, a temperature-dependent equilibrium constant for the interconversion between Eact, the active form of enzyme, and Einact, a reversibly inactive form of enzyme, the equilibrium model currently provides the most complete description of the enzyme-temperature relationship; its derived parameters are intrinsic and apparently universal and, being derived under reaction conditions, potentially have physiological significance. One of these parameters, Teq, correlates with host growth temperature better than enzyme stability does. The vent-dwelling annelid Alvinella pompejana has been reported as an extremely eurythermal organism, and the symbiotic complex microbial community associated with its dorsal surface is likely to experience similar environmental thermal conditions. The A. pompejana episymbiont community, predominantly composed of epsilonproteobacteria, has been analyzed metagenomically, enabling direct retrieval of genes coding for enzymes suitable for equilibrium model applications. Two such genes, coding for isopropylmalate dehydrogenase and glutamate dehydrogenase, have been isolated from the A. pompejana episymbionts, heterologously expressed, and shown by reverse transcription-quantitative PCR to be actively expressed. The equilibrium model parameters of characterized expression products suggested that enzyme eurythermalism constitutes part of the thermal adaptation strategy employed by the episymbionts. Moreover, the enzymes' thermal characteristics correspond to their predicted physiological roles and the abundance and expression of the corresponding genes. This paper demonstrates the use of the equilibrium model as part of a top-down metagenomic approach to studying temperature adaptation of uncultured organisms.

text: Enzymic approach to eurythermalism of Alvinella pompejana and its Episymbionts The equilibrium model, which describes the influence of temperature on enzyme activity, has been established as a valid and useful tool for characterizing enzyme eurythermalism and thermophily. By introducing Keq, a temperature-dependent equilibrium constant for the interconversion between Eact, the active form of enzyme, and Einact, a reversibly inactive form of enzyme, the equilibrium model currently provides the most complete description of the enzyme-temperature relationship; its derived parameters are intrinsic and apparently universal and, being derived under reaction conditions, potentially have physiological significance. One of these parameters, Teq, correlates with host growth temperature better than enzyme stability does. The vent-dwelling annelid Alvinella pompejana has been reported as an extremely eurythermal organism, and the symbiotic complex microbial community associated with its dorsal surface is likely to experience similar environmental thermal conditions. The A. pompejana episymbiont community, predominantly composed of epsilonproteobacteria, has been analyzed metagenomically, enabling direct retrieval of genes coding for enzymes suitable for equilibrium model applications. Two such genes, coding for isopropylmalate dehydrogenase and glutamate dehydrogenase, have been isolated from the A. pompejana episymbionts, heterologously expressed, and shown by reverse transcription-quantitative PCR to be actively expressed. The equilibrium model parameters of characterized expression products suggested that enzyme eurythermalism constitutes part of the thermal adaptation strategy employed by the episymbionts. Moreover, the enzymes' thermal characteristics correspond to their predicted physiological roles and the abundance and expression of the corresponding genes. This paper demonstrates the use of the equilibrium model as part of a top-down metagenomic approach to studying temperature adaptation of uncultured organisms.

year: 2007

title: Technology as cause of and solution to the empathy problem

authors: Weijers, Dan M.

abstract: For decades, Sherry Turkle has explored the risks and opportunities of technology for people, relationships, and society. In The Second Self (1984), Turkle emphasised the positive potential of digital technologies and computer games. But since then, her work has increasingly documented the risks of technology as they have crystallised into tangible harms. Culminating in her recent memoir, The Empathy Diaries (2021), Turkle’s oeuvre is best viewed as a warning that our increasing use of ICTs, and reliance on smartphones in particular, is causing usto become less empathetic.Here,we acknowledge Turkle’s warning and use her own earlier technological optimism to investigate potential technological solutions to the emerging empathy problem.

text: Technology as cause of and solution to the empathy problem For decades, Sherry Turkle has explored the risks and opportunities of technology for people, relationships, and society. In The Second Self (1984), Turkle emphasised the positive potential of digital technologies and computer games. But since then, her work has increasingly documented the risks of technology as they have crystallised into tangible harms. Culminating in her recent memoir, The Empathy Diaries (2021), Turkle’s oeuvre is best viewed as a warning that our increasing use of ICTs, and reliance on smartphones in particular, is causing usto become less empathetic.Here,we acknowledge Turkle’s warning and use her own earlier technological optimism to investigate potential technological solutions to the emerging empathy problem.

year: 2021

title: The rhetorical organisation of Maori discourse: An illustration

authors: Crombie, Winifred

subjects: Māori medium education

abstract: Almost 20% all Māori students in New Zealand schools are involved in some form of Māori-medium education. These students need to develop competence in using the language for a wide range of purposes. They need, therefore, to understand a range of written discourse conventions. In seeking to assist them in this task, elders and scholars are turning to the works of major Māori figures of the past, works composed when the language was used widely in a range of discourse contexts. However, scholars need ways of analysing these texts and of communicating their findings to others. The primary aim of this paper is to demonstrate one such approach. A single letter of condolence written in Māori is analysed here in terms of rhetorical discourse structure. On the basis of the analysis, a number of hypotheses concerning epistolary discourse in Māori are put forward. The primary hypothesis is that letters of condolence written in Māori by highly competent users of the language are likely to be characterized by an overall Problem-Solution rhetorical prototype involving spiral multilayering.

text: The rhetorical organisation of Maori discourse: An illustration Almost 20% all Māori students in New Zealand schools are involved in some form of Māori-medium education. These students need to develop competence in using the language for a wide range of purposes. They need, therefore, to understand a range of written discourse conventions. In seeking to assist them in this task, elders and scholars are turning to the works of major Māori figures of the past, works composed when the language was used widely in a range of discourse contexts. However, scholars need ways of analysing these texts and of communicating their findings to others. The primary aim of this paper is to demonstrate one such approach. A single letter of condolence written in Māori is analysed here in terms of rhetorical discourse structure. On the basis of the analysis, a number of hypotheses concerning epistolary discourse in Māori are put forward. The primary hypothesis is that letters of condolence written in Māori by highly competent users of the language are likely to be characterized by an overall Problem-Solution rhetorical prototype involving spiral multilayering.

year: 2001-02