Biology subjects

Egger, K.

Publications and source records attributed to Egger, K..

3 recordsLinked to original sources

bioRxiv2022

Never let me down: Optimizing performance of serum free culture medium for bovine satellite cells

Cultivated meat may be a more ethical, environmentally friendly, antibiotic-free meat alternative of the future. As of now, one of the main limiting factors for bringing cultivated meat to the market is the high cost of the cell culture media and their great dependency on serum albumins, production of which is predicted to become a major bottleneck of this industry. Here, using bovine muscle stem cells (BSC) we optimized B8/B9 medium - one of the well-established serum free, fully defined medium compositions available for purchase or for preparation in-house. We show several combinations of the growth factors/myokines/hormones, which were able to substantially increase BSCs proliferation rate, as well as treatment schemes allowing for five to ten times lower concentrations of signaling molecules for the same effect. Additionally, we identified several food grade, low-price medium stabilizers, exhibiting comparable or even superior stabilization of the B8 medium in short-term cultivations, as compared to recombinant human serum albumin (HSA). DoE aided in identifying the best cultivation conditions. Other satellite cells (porcine, chicken and fish) were grown in several final cell culture medium compositions, showing significant cell-line specific differences in performance. Also, the proliferation and yield of CHO cell line, which is relevant e.g. for the production of growth factors, was also successfully increased using our stabilization approach. We conclude that stabilizers tested here can act as versatile low-cost medium additives, partly by prolonging the half-life of growth factors. Thus, we provide an alternative to HSA, enabling up to an overall 73% reduction of medium price.

cell biology↗

bioRxiv2021

Topology and contribution to the pore channel lining of plasma membrane-embedded S. flexneri type 3 secretion translocase IpaB

Shigella spp. are human bacterial pathogens that cause bacillary dysentery. Virulence depends on a type 3 secretion system (T3SS), a highly conserved structure present in multiple important human and plant pathogens. Upon host cell contact, the T3SS translocon is delivered to the host membrane, facilitates bacterial docking to the membrane, and enables delivery of effector proteins into the host cytosol. The Shigella translocon is composed of two proteins, IpaB and IpaC, which together form this multimeric structure within host plasma membranes. Upon interaction of IpaC with host intermediate filaments, the translocon undergoes a conformational change that allows for bacterial docking onto the translocon and, together with host actin polymerization, enables subsequent effector translocation through the translocon pore. To generate additional insights into the translocon, we mapped the topology of IpaB in plasma membrane-embedded pores using cysteine substitution mutagenesis coupled with site-directed labeling and proximity-enabled crosslinking by membrane permeant sulfhydryl reactants. We demonstrate that IpaB function is dependent on post translational modification by a plasmid-encoded acyl carrier protein. We show that the first transmembrane domain of IpaB lines the interior of the translocon pore channel such that the IpaB portion of the channel forms a funnel-like shape leading into the host cytosol. In addition, we identify regions of IpaB within its cytosolic domain that protrude into and are closely associated with the pore channel. Taken together, these results provide a framework for how IpaB is arranged within translocons natively delivered by Shigella during infection. ImportanceType 3 secretion systems are nanomachines employed by many bacteria, including Shigella, which deliver into human cells bacterial virulence proteins that alter cellular function in ways that promote infection. Delivery of Shigella virulence proteins occurs through a pore formed in human cell membranes by the proteins IpaB and IpaC. Here, we define how IpaB contributes to the formation of pores natively delivered into human cell membranes by S. flexneri. We show that a specific domain of IpaB (transmembrane domain 1) lines much of the pore channel and that portions of IpaB that lie in the inside of the human cell loop back into and/or are closely associated with the pore channel. These findings provide new insights into the organization and function of the pore in serving as the conduit for delivery of virulence proteins into human cells during Shigella infection.

microbiology↗

bioRxiv2019

Supra-threshold perception and neural representation of tones presented in noise in conditions of masking release

The neural representation and perceptual salience of tonal signals presented in different noise maskers were investigated. The properties of the maskers and signals were varied such that they produced different amounts of either monaural masking release, binaural masking release, or a combination of both. The signals were then presented at different levels above their corresponding masked thresholds and auditory evoked potentials (AEPs) were measured. It was found that, independent of the masking condition, the amplitude of the P2 component of the AEP was similar for the same stimulus levels above masked threshold, suggesting that both monaural and binaural effects of masking release were represented at the level of P2 generation. The perceptual salience of the signal was evaluated at equal levels above masked threshold using a rating task. In contrast to the electrophysiological findings, the subjective ratings of the perceptual signal salience were less consistent with the signal level above masked threshold and varied strongly across listeners and masking conditions. Overall, the results from the present study suggest that the P2 amplitude of the AEP represents an objective indicator of the audibility of a target signal in the presence of complex acoustic maskers.

neuroscience↗