Biology subjects

Holm, C.

Publications and source records attributed to Holm, C..

3 recordsLinked to original sources

bioRxiv2024

Influence of bacterial swimming and hydrodynamics on infection by phages

Bacteriophages ("phages") are viruses that infect bacteria. Since they do not actively self-propel, phages rely on thermal diffusion to find target cells--but can also be advected by fluid flows, such as those generated by motile bacteria themselves in bulk fluids. How does the flow field generated by a swimming bacterium influence how it encounters and is infected by phages? Here, we address this question using coupled molecular dynamics and lattice Boltzmann simulations of flagellated bacteria swimming through a bulk fluid containing uniformly-dispersed phages. We find that while swimming increases the rate at which both the cell body and flagellar propeller are infected by phages, hydrodynamic interactions strongly suppress this increase at the cell body, but conversely enhance this increase at the flagellar bundle. Our results highlight the pivotal influence of hydrodynamics on the interactions between bacteria and phages, as well as other diffusible species in microbial environments.

biophysics↗

bioRxiv2023

Butyrate-producing bacteria as probiotic supplement: beneficial effects on metabolism and modulation of behavior in an obesity mouse model

Obesity is a risk factor for cardio-metabolic and neurological disease. The contribution of gut microbiota to derangements of the gut-brain axis in the context of obesity has been acknowledged, particularly through physiology modulation by short-chain fatty acids (SCFAs). Thus, probiotic interventions and administration of SCFAs have been employed with the purpose of alleviating symptoms in both metabolic and neurological disease. We have tested the effects of four butyrate-producing bacteria from the Lachnospiraceae family on the development of metabolic syndrome and behavioural alterations in a mouse model of diet-induced obesity. Male mice were fed either a high-fat diet (HFD) or an ingredient-matched control diet for 2 months, and bacteria cultures or culture medium were given by gavage to HFD-fed mice every second day. Assessment of the mice through a battery of metabolic and behaviour tests revealed that one of the administered bacteria affords some degree of protection against the development of obesity and its complications.

physiology↗

bioRxiv2021

Central hormone-sensitive lipase is located at synapses and is necessary for normal memory performance in mice

Hormone-sensitive lipase (HSL) is mainly present in the adipose tissue where it hydrolyses diacylglycerol. Although brain expression of HSL has been reported, its presence in different cellular compartments is uncertain, and its role in regulating brain lipid metabolism remains hitherto unexplored. We propose that HSL has a role in regulating the availability of bioactive lipids necessary for adequate neuronal function. Therefore, we tested the hypothesis that dampening HSL activity leads to brain dysfunction. We found HSL protein and activity throughout all the mouse brain, localised in neurons and especially enriched in synapses. HSL null mice were then analysed using a battery of behavioural tests. Relative to wild-type littermates, HSL null mice showed impaired short- and long-term memory, but preserved exploratory behaviours. Molecular analysis of the cortex and hippocampus showed increased expression of genes involved in glucose utilization in the hippocampus but not cortex of HSL null mice compared to controls. Lipidomics analyses indicated an impact of HSL deletion on the profile of bioactive lipids, including endocannabinoids and eicosanoids that are known to modulate neuronal activity, cerebral blood blow and inflammation processes. Accordingly, mild increases in expression of pro-inflammatory cytokines suggest low grade inflammation in HSL null mice compared to littermates. We conclude that HSL has a homeostatic role in maintaining pools of lipids that are needed for brain function. It remains to be tested, however, whether the recruitment of HSL for the synthesis of these lipids occurs during increased neuronal activity, or whether HSL participates in neuroinflammatory responses.

neuroscience↗