Biology subjects

Gruber, A.

Publications and source records attributed to Gruber, A..

3 recordsLinked to original sources

bioRxiv2018

Muscle mechanics and energy expenditure of the triceps surae during rearfoot and forefoot running

Forefoot running is advocated to improve running economy because of increased elastic energy storage than rearfoot running. This claim has not been assessed with methods that predict the elastic energy contribution to positive work or estimate muscle metabolic cost. The purpose of this study was to compare the mechanical work and metabolic cost of the gastrocnemius and soleus between rearfoot and forefoot running. Seventeen rearfoot and seventeen forefoot runners ran over-ground with their habitual footfall pattern (3.33-3.68m*s-1) while collecting motion capture and ground reaction force data. Ankle and knee joint angles and ankle joint moments served as inputs into a musculoskeletal model that calculated the mechanical work and metabolic energy expenditure of each muscle using Hill-based muscle models with contractile (CE) and series elastic (SEE) elements. A mixed-factor ANOVA assessed the difference between footfall patterns and groups (=0.05). Forefoot running resulted in greater SEE mechanical work in the gastrocnemius than rearfoot running but no differences were found in CE mechanical work or CE metabolic energy expenditure. Forefoot running resulted in greater soleus SEE and CE mechanical work and CE metabolic energy expenditure than rearfoot running. The metabolic cost associated with greater CE velocity, force production, and activation during forefoot running may outweigh any metabolic energy savings associated with greater SEE mechanical work. Therefore, there was no energetic benefit at the triceps surae for one footfall pattern or the other. The complex CE-SEE interactions must be considered when assessing muscle metabolic cost, not just the amount of SEE strain energy.

bioengineering↗

bioRxiv2018

Description and charactrization of the Amazonian entomopathogenic bacterium Photorhabdus luminescens MN7

Many isolates of the genus Photorhabdus have been reported around the world. Here we describe the first Brazilian Photorhabdus isolate, found in association with the entomopathogenic nematode Heterorhabditis baujardi LPP7, from the Amazonian forest in Monte Negro (RO, Brazil). The new isolate can be grouped with the Hb-Hm clade of P. luminescens subsp. luminescens, close to the new subspecies P. luminescens subsp. sonorensis. P. luminescens MN7 has several characteristics expected of variant form I cells, such as the presence of intracellular crystals, secretion of hydrolytic enzymes (lipases and proteases) and bioluminescence. Although H. baujardi LPP7 is not prolific when compared to H. bacteriophora HP88, P. luminescens MN7 is clearly pathogenic and probably secretes the same toxins as P. luminescens subsp. luminescens W14, when fed to larvae of the greater wax moth Galleria mellonella. This behavior is different from what is found in Photorhabdus luminescens subsp. laumondii HP88, which was used as a control in our experiments, and P. l. subsp. laumondii TT01. Besides the toxin secretion, P. luminescens MN7 secretes proteolytic polypeptides that have molecular masses different from those found in P. l. subsp. laumondii TT01. Finally, the crude extract from spent culture medium was shown to contain 3,5-dihydroxy-4-isopropyl-cis-stilbene and 1,3,8-trihydroxy-9,10-anthraquinone as the major compounds, similarly to other Photorhabdus luminescens strains.

microbiology↗

bioRxiv2018

Mitochondrial targeting of glycolysis in a major lineage of eukaryotes

Glycolysis is a major cytosolic catabolic pathway that provides ATP for many organisms1. Mitochondria play an even more important role in the provision of additional cellular ATP for eukaryotes2. Here, we show that in many stramenopiles, the C3 part of glycolysis is localised in mitochondria. We discovered genuine mitochondrial targeting signals on the six last enzymes of glycolysis. These targeting signals are recognised and sufficient to import GFP into mitochondria of a heterologous host. Analysis of eukaryotic genomes identified these targeting signals on many glycolytic C3 enzymes in a large group of eukaryotes found in the SAR supergroup3, in particular the stramenopiles. Stramenopiles, or heterokonts, are a large group of ecologically important eukaryotes that includes multi- and unicellular algae such as kelp and diatoms, but also economically important oomycete pathogens such as Phytophthora infestans. Confocal immunomicroscopy confirmed the mitochondrial location of glycolytic enzymes for the human parasite Blastocystis. Enzyme assays on cellular fractions confirmed the presence of the C3 part of glycolysis in Blastocystis mitochondria. These activities are sensitive to treatment with proteases and Triton X-100 but not proteases alone. Our work clearly shows that core cellular metabolism is more plastic than previously imagined and suggests new strategies to combat stramenopile pathogens such as the causative agent of late potato blight, P. infestans.

evolutionary biology↗