title: Summer variability, winter dormancy: lichen activity over 3 years at Botany Bay, 77°S latitude, continental Antarctica

authors: Schroeter, Burkhard

subjects: snall fall

abstract: Lichens make up a major component of Antarctic vegetation; they are also poikilohydric and are metabolically active only when hydrated. Logistic constraints have meant that we have little idea of the length, timing or environmental conditions of activity periods of lichens. We present the results of a three-year monitoring of the activity of the lichen Umbilicaria aprina at Botany Bay (77° S latitude) in the Ross Sea region, continental Antarctica. Chlorophyll fluorescence parameters that allowed hydrated metabolic activity to be detected were recorded with a special fluorometer at 2- or 3-h intervals. Air and thallus temperatures and incident PPFD (photosynthetic photon flux density, lmol photon m-2 s-1) were also recorded at hourly intervals. Activity was extremely variable between months and years and, overall, lichen was active for 7% of the 28-month period. Spring snow cover often delayed the onset of activity. Whereas the period immediately after snow melt was often very productive, the later months, January to March, often showed low or no activity. Mean thallus temperature when active was just above zero degrees and much higher than the annual mean air temperature of -15 to -19° C. Because major snow melts occurred when incident radiation was high, the lichen was also subjected to very high PPFD when active, often more than 2,500 lmol photon m⁻² s⁻¹. The major environmental stress appeared to be high light rather than low temperatures, and the variability of early season snow fall means that prediction of activity will be very difficult.

text: Summer variability, winter dormancy: lichen activity over 3 years at Botany Bay, 77°S latitude, continental Antarctica Lichens make up a major component of Antarctic vegetation; they are also poikilohydric and are metabolically active only when hydrated. Logistic constraints have meant that we have little idea of the length, timing or environmental conditions of activity periods of lichens. We present the results of a three-year monitoring of the activity of the lichen Umbilicaria aprina at Botany Bay (77° S latitude) in the Ross Sea region, continental Antarctica. Chlorophyll fluorescence parameters that allowed hydrated metabolic activity to be detected were recorded with a special fluorometer at 2- or 3-h intervals. Air and thallus temperatures and incident PPFD (photosynthetic photon flux density, lmol photon m-2 s-1) were also recorded at hourly intervals. Activity was extremely variable between months and years and, overall, lichen was active for 7% of the 28-month period. Spring snow cover often delayed the onset of activity. Whereas the period immediately after snow melt was often very productive, the later months, January to March, often showed low or no activity. Mean thallus temperature when active was just above zero degrees and much higher than the annual mean air temperature of -15 to -19° C. Because major snow melts occurred when incident radiation was high, the lichen was also subjected to very high PPFD when active, often more than 2,500 lmol photon m⁻² s⁻¹. The major environmental stress appeared to be high light rather than low temperatures, and the variability of early season snow fall means that prediction of activity will be very difficult.

year: 2011

title: The Biochemistry of VapBC Toxin-Antitoxins

authors: McKenzie, Joanna Leigh

subjects: Biochemistry

abstract: The VapBC toxin-antitoxin (TA) systems were first identified in 2005 and little is known about their contemporary biological function, despite the fact that VapBC TAs are the largest TA family and are widespread in bacteria and archaea (Arcus, Rainey, & Turner, 2005; Gerdes, Christensen, & Lobner-Olsen, 2005). Mycobacterium tuberculosis has a surprisingly large repertoire of 45 VapBC TAs. In contrast Mycobacterium smegmatis, a model organism for M. tuberculosis, contains only one vapBC operon, thereby making it an ideal system to uncover the possible role(s) that VapBC proteins play in mycobacteria. This thesis describes the functional characterisation of VapC from M. smegmatis and two homologues from Pyrobaculum aerophilum, along with biophysical characterisation of the VapBC complex from M. smegmatis. The VapBC proteins from M. smegmatis form a tight complex in a 1:1 ratio and interactions between the proteins result in a tetramer of VapBC heterodimers. VapB is susceptible to proteolytic degradation when not bound to DNA thus hinting at a mechanism for VapC activation.
VapC proteins from P. aerophilum (VapCPAE2754 and VapCPAE0151) and VapC from M. smegmatis display Mg²⁺/Mn²⁺ dependent, sequence specific ribonuclease activity. VapC from M. smegmatis targets the AU rich sequences AUAU and AUAA. Whereas VapCPAE2754 and VapCPAE0151 from P. aerophilum both target GGUG and GGGG sequences. These sequences are present in over half the mRNA transcripts encoded in the P. aerophilum genome, making them potent toxins. VapC ribonuclease activity is inhibited when VapC is bound to VapB. When VapC is released from the VapBC complex it cleaves cohorts of mRNA transcripts thereby reducing protein synthesis for this cohort of genes. Microarray analysis revealed that the majority of transcripts downregulated in response to VapC expression in M. smegmatis are involved in carbon utilisation and transport (Robson, 2010). Bioinformatics shows that the target sequence is overrepresented in the downregulated transcripts. The majority of the downregulated genes are in operons, which suggests a mechanism for destabilising mRNA transcripts to regulate specific metabolic processes.

text: The Biochemistry of VapBC Toxin-Antitoxins The VapBC toxin-antitoxin (TA) systems were first identified in 2005 and little is known about their contemporary biological function, despite the fact that VapBC TAs are the largest TA family and are widespread in bacteria and archaea (Arcus, Rainey, & Turner, 2005; Gerdes, Christensen, & Lobner-Olsen, 2005). Mycobacterium tuberculosis has a surprisingly large repertoire of 45 VapBC TAs. In contrast Mycobacterium smegmatis, a model organism for M. tuberculosis, contains only one vapBC operon, thereby making it an ideal system to uncover the possible role(s) that VapBC proteins play in mycobacteria. This thesis describes the functional characterisation of VapC from M. smegmatis and two homologues from Pyrobaculum aerophilum, along with biophysical characterisation of the VapBC complex from M. smegmatis. The VapBC proteins from M. smegmatis form a tight complex in a 1:1 ratio and interactions between the proteins result in a tetramer of VapBC heterodimers. VapB is susceptible to proteolytic degradation when not bound to DNA thus hinting at a mechanism for VapC activation.
VapC proteins from P. aerophilum (VapCPAE2754 and VapCPAE0151) and VapC from M. smegmatis display Mg²⁺/Mn²⁺ dependent, sequence specific ribonuclease activity. VapC from M. smegmatis targets the AU rich sequences AUAU and AUAA. Whereas VapCPAE2754 and VapCPAE0151 from P. aerophilum both target GGUG and GGGG sequences. These sequences are present in over half the mRNA transcripts encoded in the P. aerophilum genome, making them potent toxins. VapC ribonuclease activity is inhibited when VapC is bound to VapB. When VapC is released from the VapBC complex it cleaves cohorts of mRNA transcripts thereby reducing protein synthesis for this cohort of genes. Microarray analysis revealed that the majority of transcripts downregulated in response to VapC expression in M. smegmatis are involved in carbon utilisation and transport (Robson, 2010). Bioinformatics shows that the target sequence is overrepresented in the downregulated transcripts. The majority of the downregulated genes are in operons, which suggests a mechanism for destabilising mRNA transcripts to regulate specific metabolic processes.

year: 2011

title: Rock-a-bye Baby: Infant care and parenting around sleep

authors: Jones, Horiana Majorie

subjects: Infant Sleep

abstract: This research is a part of a wider international study which explores infant sleep amongst various ethnicities and cultures. This study has explored infant sleep practices in New Zealand, with a specific focus on Māori child rearing practices. This study aimed to firstly, explore what techniques Māori parents use to get their ppi to sleep (2 months- 2 years of age). Secondly, this study aimed to understand the various factors that influence parents’ decisions to use their particular method e.g. Parent assisted approaches (rocking, co-sleeping, bed sharing breastfeeding to sleep), or self-soothing infant sleep methods (cry it out, controlled comforting). Mixed methods were used to collect the data for this study. Overall, 562 primary caregivers/parents completed the survey component of this study with 11 percent identifying as Māori. A further 10 were taken from the survey sample and participated in face to face interviews.  
The results show that parent assisted techniques such as rocking, lying down with baby, and feeding to sleep were the most practiced approach to infant sleep for Māori whanau across the survey and interview findings. Participants within the interview study that used parent assisted techniques to initiate infant sleep were also more likely to bed-share with their babies. Self- soothing techniques such as controlled comforting and cry it out were practiced by a number of parents within the survey and interview groups The findings from this study suggest that a number of different factors influence parenting style. Survey data found that culture, books, magazines, online material and advice from family were the most influential factors in parenting styles. The interviews findings suggest that the convenience of an approach, whanau influence, being a parent of more than one child, environmental factors, healthcare recommendations, safety and culture all influenced aspects of their approaches to infant sleep.

text: Rock-a-bye Baby: Infant care and parenting around sleep This research is a part of a wider international study which explores infant sleep amongst various ethnicities and cultures. This study has explored infant sleep practices in New Zealand, with a specific focus on Māori child rearing practices. This study aimed to firstly, explore what techniques Māori parents use to get their ppi to sleep (2 months- 2 years of age). Secondly, this study aimed to understand the various factors that influence parents’ decisions to use their particular method e.g. Parent assisted approaches (rocking, co-sleeping, bed sharing breastfeeding to sleep), or self-soothing infant sleep methods (cry it out, controlled comforting). Mixed methods were used to collect the data for this study. Overall, 562 primary caregivers/parents completed the survey component of this study with 11 percent identifying as Māori. A further 10 were taken from the survey sample and participated in face to face interviews.  
The results show that parent assisted techniques such as rocking, lying down with baby, and feeding to sleep were the most practiced approach to infant sleep for Māori whanau across the survey and interview findings. Participants within the interview study that used parent assisted techniques to initiate infant sleep were also more likely to bed-share with their babies. Self- soothing techniques such as controlled comforting and cry it out were practiced by a number of parents within the survey and interview groups The findings from this study suggest that a number of different factors influence parenting style. Survey data found that culture, books, magazines, online material and advice from family were the most influential factors in parenting styles. The interviews findings suggest that the convenience of an approach, whanau influence, being a parent of more than one child, environmental factors, healthcare recommendations, safety and culture all influenced aspects of their approaches to infant sleep.

year: 2017