Biology subjects

Jespersen, L.

Publications and source records attributed to Jespersen, L..

2 recordsLinked to original sources

bioRxiv2025

A chemically defined medium to support the growth of food-relevant Bacillus species

The Bacillus genus contains many members with food significance, including the food-grade Bacillus subtilis clade often used in fermentations and the pathogenic Bacillus cereus clade. Chemically defined media for Bacillus species are crucial tools to allow detailed investigations of the influence of specific nutrients on growth and also improve reproducibility and consistency of experiments. Previous studies have focused on the development of defined media for single species, while the aim of this study was to develop a chemically defined medium that supports the growth of multiple food relevant Bacillus species. The new medium, Pafoba, was tested using two pathogenic strains of the Bacillus cereus clade and eleven strains of the Bacillus subtilis clade representing seven different clade members. All thirteen Bacillus strains were able to grow on Pafoba, of which ten displayed a similar or higher maximum OD600 on Pafoba medium compared to rich medium (Brain Heart Infusion broth). Detailed analysis revealed a biotin requirement for Bacillus subtilis strain PRO64, and the necessity of including essential amino acids for Bacillus weihenstephanensis and Bacillus cereus strains. In conclusion, the chemically defined Pafoba medium provides a controlled and reproducible growth environment for fundamental studies and is suitable for detection and enumeration of a broad range of Bacillus spp. related to food processing and safety. ImportanceBacillus species are important in both food fermentation and food safety. While members of the Bacillus subtilis clade are used in the production of fermented foods, those in the Bacillus cereus group are associated with foodborne illness. This study presents a chemically defined medium that supports the growth of multiple food-relevant Bacillus species, enabling precise control over nutrient composition. Knowledge of Bacillus cereus metabolism under defined conditions is essential to support efforts in food safety, risk assessment, and the development of targeted intervention strategies. Likewise, an understanding of Bacillus subtilis metabolism under defined conditions is essential to optimize fermentation processes, improve product consistency, and enhance functional food development. By providing a standardized and reproducible growth environment, the medium developed in this study will facilitate research that advances both microbial food safety and the controlled use of beneficial Bacillus strains in food production.

microbiology↗

bioRxiv2023

Hebbian priming of human spinal motor learning

Learning or relearning of motor skills requires plasticity in relevant neural circuits. Motor recovery following lesions to the corticospinal system can be augmented through neuromodulation techniques targeting the affected or compensatory neural circuits. By repeatedly pairing transcranial magnetic stimulation of the primary motor cortex (M1) and motoneuronal electrical stimulation (i.e., paired corticomotoneuronal stimulation, PCMS) timed to arrive at the corticomotoneuronal (CM) synapses in close temporal proximity, spike-timing-dependent bidirectional changes in CM transmission can be induced in humans (Taylor & Martin, 2009). PCMS-induced increases in CM transmission have been demonstrated to transiently improve motor control in patients with spinal cord injury (Bunday & Perez 2012), whereas effects on the malleability of neural circuits are entirely unexplored. We hypothesized that PCMS can prime mechanisms of subsequent motor learning exclusively when directed to the neural circuitry underpinning the motor behavior. In three experiments, we provide the first evidence ( Experiment I) and a double-blinded, sham-controlled replication ( Experiment II) that PCMS targeting the spinal CM synapses can prime subsequent learning of rapid finger movements relying on spinal neuroplasticity. Finally, we demonstrate that the effects of PCMS are circuit-specific and bidirectional. When PCMS was timed to arrive at a facilitatory interval in M1 but an inhibitory interval at the CM synapses subsequent learning was transiently impeded ( Experiment III). Taken together, our results provide proof-of-principle that non-invasively induced plasticity governed by Hebbian learning rules interacts with experience-dependent plasticity in the spinal cord with positive implications for motor learning. Our results offer a mechanistic rationale for priming sensorimotor training with individualized PCMS to enhance the effects of motor practice in neurorehabilitation. HighlightsO_LIPaired corticomotoneuronal stimulations (PCMS) promote ballistic motor learning and facilitate corticospinal excitability compared to rest and sham protocols. C_LIO_LIA double-blinded sham experiment replicates priming effects of PCMS on ballistic motor learning and demonstrates long-term benefits of combined PCMS and motor practice. C_LIO_LIThe facilitating effect of PCMS on ballistic motor learning is circuit-specific with superior effects on ballistic motor learning after facilitating PCMS compared to control protocols. C_LI

neuroscience↗