Biology subjects

Grimaud, J.

Publications and source records attributed to Grimaud, J..

6 recordsLinked to original sources

bioRxiv2026

An Innovative, Low-Cost Medium for the Bioproduction of Prodigiosin by Serratia marcescens.

Prodigiosin is a red pigment produced by various bacteria, including Serratia marcescens. Despite its wide and promising range of biological activities, the large-scale production of prodigiosin is currently limited by its high cost and low yields. Here we propose and optimize an innovative, low-cost, peanut-based solid culture medium that enhances the yield of prodigiosin produced by Serratia marcescens. Colorimetric assays revealed that peanut significantly stimulates prodigiosin synthesis. Further HPLC-MS analysis allowed us to unambiguously identify prodigiosin and shows that our medium specifically improves the yield of prodigiosin. Overall, our innovative culture medium could help lower prodigiosin production costs and, ultimately, open new industrial applications.

bioengineering↗

bioRxiv2022

Learning-dependent evolution of odor mixture representations in piriform cortex

Rodents can learn from exposure to rewarding odors to make better and quicker decisions. The piriform cortex is thought to be important for learning complex odor associations, however it is not understood exactly how it learns to remember discriminations between many, sometimes overlapping, odor mixtures. We investigated how odor mixtures are represented in the posterior piriform cortex (pPC) of mice while they learn to discriminate a unique target odor mixture against hundreds of nontarget mixtures. We find that a significant proportion of pPC neurons discriminate between the target and all other nontarget odor mixtures. Neurons that prefer the target odor mixture tend to respond with brief increases in firing rate at odor onset compared to other neurons, which exhibit sustained and/or decreased firing. We allowed mice to continue training after they had reached high levels of performance and find that pPC neurons become more selective for target odor mixtures as well as for randomly chosen repeated nontarget odor mixtures that mice did not have to discriminate from other nontargets. These single unit changes during overtraining are accompanied by better categorization decoding at the population level, even though behavioral metrics of mice such as reward rate and latency to respond do not change. However, when difficult ambiguous trial types are introduced, the robustness of the target selectivity is correlated with better performance on the difficult trials. Taken together, these data reveal pPC as a dynamic and robust system that can optimize for both current and possible future task demands at once.

neuroscience↗

bioRxiv2022

Antifungal activity of Cinnamomum cassia and Origanum compactum essential oils against Aspergillus oryzae

Aspergillosis is a nosocomial disease that usually affects the respiratory system. While most patients develop mild symptoms, aspergillosis can become a serious health threat in immunocompromised populations and patients with pre-existing respiratory conditions. Aspergillosis is caused by fungi of the Aspergillus genus. Existing treatments include drugs such as amphotericin B, with strong side effects. Numerous studies have shown the antifungal properties of essential oils (EOs), which represent potential alternative treatments against fungal infections. Here, we screened the antifungal properties of five EOs against Aspergillus oryzae: Melaleuca alternifolia, Mentha x piperita, Thymus zygis, Origanum compactum, and Cinnamomum cassia. Of the five EOs, two demonstrated antifungal activity: Origanum compactum acted as a fungistatic, while Cinnamomum cassia showed both fungistatic and fungicidal effects against A. oryzae. Therefore, both EOs represent potential alternative treatments against Aspergillosis.

microbiology↗

bioRxiv2020

Bilateral alignment of receptive fields in the olfactory cortex points to non-random connectivity

Each olfactory cortical hemisphere receives ipsilateral odor information directly from the olfactory bulb and contralateral information indirectly from the other cortical hemisphere. Since neural projections to the olfactory cortex are disordered and non-topographic, spatial information cannot be used to align projections from the two sides like in the visual cortex. Therefore, how bilateral information is integrated in individual cortical neurons is unknown. We have found, in mice, that the odor responses of individual neurons to selective stimulation of each of the two nostrils are highly matched, such that odor identity decoding optimized with information arriving from one nostril transfers very well to the other side. Remarkably, these aligned responses are nevertheless asymmetric enough to allow decoding of stimulus laterality. Computational analysis shows that such matched odor tuning is incompatible with purely random connections but is explained readily by Hebbian plasticity structuring bilateral connectivity. Our data reveal that despite the distributed and fragmented sensory representation in the olfactory cortex, odor information across the two hemispheres is highly coordinated.

neuroscience↗

bioRxiv2018

Calcium-activated chloride channels clamp odor-evoked spike activity in olfactory receptor neurons

The calcium-activated chloride channel anoctamin-2 (Ano2) is thought to amplify transduction currents in ORNs, a hypothesis supported by previous studies in dissociated neurons from Ano2-/- mice. Paradoxically, despite a reduction in transduction currents in Ano2-/- ORNs, their spike output for odor stimuli may be higher. We examined the role of Ano2 in ORNs in their native environment in freely breathing mice by imaging activity in ORN axons as they arrive in the olfactory bulb glomeruli. Odor-evoked responses in ORN axons of Ano2-/- mice were consistently larger for a variety of odorants and concentrations. In an open arena, Ano2-/- mice took longer to approach a localized odor source than wild-type mice, revealing clear olfactory behavioral deficits. Our studies provide the first in vivo evidence toward an alternative role for Ano2 in the olfactory transduction cascade, where it may serve as a feedback mechanism to clamp ORN spike output.

neuroscience↗

bioRxiv2017

Distinct projection patterns of different classes of layer 2 principal neurons in the olfactorycortex

Processing of olfactory information in the anterior piriform cortex (APC) is widely thought to be non-topographic due to distributed projections from the olfactory bulb (OB). Layer 2 principal neurons in the APC can be divided into 2 subtypes: semilunar (SL) and superficial pyramidal (SP) cells. Although it is known that SL and SP cells receive differential inputs from the OB, little is known about their projection pattern to downstream structures, such as the posterior piriform cortex (PPC). Here we examined feedforward and feedback axonal projections of SL and SP cells using a combination of mouse genetics, and retrograde labeling. Retrograde tracing from the OB or PPC showed that the APC projects to these higher and lower brain regions mainly through layer 2b cells, while dual-labeling revealed a sizeable fraction of cells extending collaterals to both target regions. Furthermore, a transgenic mouse line specifically labeling SL cells showed that they send profuse axonal projections to olfactory cortical areas, but not to the OB. These findings support a model in which information flow from SL to SP cells and back to the OB forms a hierarchical feedback circuit whereas the two cell types process recurrent and feedforward information in a parallel manner.

neuroscience↗