Frenkel, A. | Search bioRxiv

bioRxiv2022

Cell specialization in cyanobacterial biofilm development revealed by expression of a cell-surface and extracellular matrix protein

Cyanobacterial biofilms are ubiquitous and play important roles in diverse environments, yet, understanding of the processes underlying development of these aggregates is just emerging. Here we report cell specialization in formation of Synechococcus elongatus PCC 7942 biofilms - a hitherto unknown characteristic of cyanobacterial multicellularity. We show that only a quarter of the cell population expresses at high levels the four-gene ebfG-operon that is required for biofilm formation. Almost all cells, however, are assembled in the biofilm. Detailed characterization of EbfG4 encoded by this operon revealed cell-surface localization as well as its presence in the biofilm matrix. Moreover, EbfG1-3 were shown to form amyloid structures such as fibrils and are thus likely to contribute to the matrix structure. These data suggest a beneficial division of labour during biofilm formation where only some of the cells allocate resources to produce matrix proteins - public goods that support robust biofilm development by the majority of the cells. Additionally, previous studies revealed the operation of a self-suppression mechanism that depends on an extracellular inhibitor, which supresses transcription of the ebfG-operon. Here we revealed inhibitor activity at an early growth stage and its gradual accumulation along the exponential growth phase in correlation with cell density. Data, however, do not support a threshold-like phenomenon known for quorum-sensing in heterotrophs. Together, data presented here demonstrate cell specialization and imply density-dependent regulation thereby providing novel insights into cyanobacterial communal behaviour. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=98 SRC="FIGDIR/small/498973v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@7758f8org.highwire.dtl.DTLVardef@172396aorg.highwire.dtl.DTLVardef@176612org.highwire.dtl.DTLVardef@2e320c_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2020

Liquid foam therapy (LiFT) for homogenous distribution of exogenous pulmonary surfactant in ARDS

Lung surfactant dysfunction has a critical role in the pathophysiology of acute respiratory distress syndrome (ARDS). Yet, efforts to treat ARDS patients with liquid instillations of exogenous surfactant have so far failed. One of the ongoing challenges in surfactant therapy is obtaining a homogeneous distribution of surfactant within the lungs despite an inherent tendency to non-uniform spreading, owing amongst others to the influence of gravity. Here, we show that liquid foam therapy (LiFT), where surfactant is foamed prior to intratracheal administration, may improve notably surfactant distribution while maintaining safety and efficacy. We first show quantitatively that a foamed surrogate surfactant solution distributes more uniformly in ex vivo pig lungs compared to endotracheal instillations of the liquid solution, while maintaining pulmonary airway pressures within a safe range. Next, we demonstrate that a foamed commercial surfactant preparation (Infasurf) is effective in an established in vivo rat lung lavage model of ARDS. Our results suggest that LiFT may be more effective than liquid instillations for treating ARDS and serve as a proof-of-principle towards large animal and clinical trials.

pharmacology and toxicology↗