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Slime : a natural history
Takes readers on a sticky scientific adventure through the three-billion-year history of slime, exploring its part in the evolution of life and its cultural and emotional significance, from its starring role in the horror genre to its subtle influence on Art Nouveau. - - Source other than the Library of Congress
Book
Assembly and dynamic regulation of the tip filament of the Bordetella type III secretion system injectisome
Bordetella bronchiseptica and Bordetella pertussis are two closely related respiratory pathogens that employ their T3SS injectisome to deliver the BteA effector into host cells. In this study, we visualized the needle tip filament of their T3SS injectisome, a structure formed by the Bsp22 protein. We demonstrate that during Bordetella cultivation in Stainer-Scholte medium, Bsp22 filaments are abundant and can dynamically extend up to several micrometers in length through the incorporation of new subunits at their distal ends. In contrast, these filaments become shorter and/or less abundant during infection of host cells. This reduction correlates with decreased bsp22 mRNA expression and lower Bsp22 protein levels, while the levels of bscD mRNA, which encodes the inner membrane ring protein of the injectisome, remain stable. These results highlight the adaptability of the Bordetella T3SS injectisome and show how its tip filament structure changes in response to different environments.
Journal Article
The slime book
\"What kind of fish uses a slime sleeping bag? Which plants capture insects with slime? Find out the answers to these questions and more in this fascinating book about slime!\"-- Publisher's description.
Book
Type VIIb secretion system recruits the dedicated cell wall hydrolase EssH to enable effector secretion by Staphylococcus aureus
Staphylococcus aureus is a leading cause of infections worldwide. S. aureus utilizes a specialized type VIIb secretion system (T7SSb) to persist in the infected host tissues as well as target competitor bacteria to establish its niche. T7SSb assembles into a multiprotein translocation complex and facilitates secretion of a set of small proteins and larger polymorphic toxins across the cytosolic membrane. Beyond the membrane, secreted proteins were thought to diffuse through the thick yet porous cell wall and release into the environment. Here, we demonstrate for the first time that S. aureus T7SSb extends across the cell wall via its EsaA subunit. Furthermore, accommodation of EsaA within the cell wall requires an associated cell wall hydrolase EssH and is essential for protein secretion via T7SSb. Thus, our findings provide a mechanistic insight for a coordinated cell wall processing and T7SSb assembly to support specialized protein secretion in S. aureus .
Journal Article
My messy body
Explores the sometimes yucky functions of the body: why are vomit, pus, and snot sometimes good for us? And yes, pee and poo are also on the list.
Book
Phenotypic, Functional, and Plasticity Features of Classical and Alternatively Activated Human Macrophages
Abstract
Macrophages are dynamic cells that mature under the influence of signals from the local microenvironment into either classically (M1) or alternatively (M2) activated macrophages with specific functional and phenotypic properties. Although the phenotypic identification of M1 and M2 macrophages is well established in mice, this is less clear for human macrophages. In addition, the persistence and reversibility of polarized human phenotypes is not well established. Human peripheral blood monocytes were differentiated into uncommitted macrophages (M0) and then polarized to M1 and M2 phenotypes using LPS/IFN-γ and IL-4/IL-13, respectively. M1 and M2 were identified as CD64+CD80+ and CD11b+CD209+, respectively, by flow cytometry. Polarized M1 cells secreted IP-10, IFN-γ, IL-8, TNF-α, IL-1β, and RANTES, whereas M2 cells secreted IL-13, CCL17, and CCL18. Functionally, M2 cells were highly endocytic. In cytokine-deficient medium, the polarized macrophages reverted back to the M0 state within 12 days. If previously polarized macrophages were given the alternative polarizing stimulus after 6 days of resting in cytokine-deficient medium, a switch in polarization was seen (i.e., M1 macrophages switched to M2 and expressed CD11b+CD209+ and vice versa). In summary, we report phenotypic identification of human M1 and M2 macrophages, their functional characteristics, and their ability to be reprogrammed given the appropriate stimuli.
Journal Article
TssW-PpkA-Fha axis controls the positioning and initiation of the type VI secretion system in Acidovorax citrulli
How cells determine where to assemble a macromolecular complex is a fundamental question in biology since the localization of these complexes is directly linked to functions. In bacteria, the type VI secretion system (T6SS) relies on effective positioning to target competitor and host cells in contact-dependent interactions. This study identifies a PpkA-TssW-Fha axis that orchestrates T6SS localization and activation through membrane anchoring and liquid-liquid phase separation at the inner membrane interface. These new insights can help us not only better understand how the T6SS functions but also better design T6SS-based solutions for therapeutic targeting of drug-resistant and T6SS-susceptible bacterial and fungal pathogens.
Journal Article
Two-Partner Secretion: Combining Efficiency and Simplicity in the Secretion of Large Proteins for Bacteria-Host and Bacteria-Bacteria Interactions
Initially identified in pathogenic Gram-negative bacteria, the two-partner secretion (TPS) pathway, also known as Type Vb secretion, mediates the translocation across the outer membrane of large effector proteins involved in interactions between these pathogens and their hosts. More recently, distinct TPS systems have been shown to secrete toxic effector domains that participate in inter-bacterial competition or cooperation. The effects of these systems are based on kin vs. non-kin molecular recognition mediated by specific immunity proteins. With these new toxin-antitoxin systems, the range of TPS effector functions has thus been extended from cytolysis, adhesion, and iron acquisition, to genome maintenance, inter-bacterial killing and inter-bacterial signaling. Basically, a TPS system is made up of two proteins, the secreted TpsA effector protein and its TpsB partner transporter, with possible additional factors such as immunity proteins for protection against cognate toxic effectors. Structural studies have indicated that TpsA proteins mainly form elongated β helices that may be followed by specific functional domains. TpsB proteins belong to the Omp85 superfamily. Open questions remain on the mechanism of protein secretion in the absence of ATP or an electrochemical gradient across the outer membrane. The remarkable dynamics of the TpsB transporters and the progressive folding of their TpsA partners at the bacterial surface in the course of translocation are thought to be key elements driving the secretion process.
Journal Article
Interplay between SpaO variants shapes the architecture of the Salmonella type III secretion sorting platform
Salmonella enterica is an increasing global public health threat. As part of its virulence arsenal, Salmonella relies on a type III secretion system (T3SS) or injectisome, a molecular injection device that translocates effector proteins into host cells to promote invasion and inflammation. A central component of this machine is the SpaO protein, which is produced in two forms: a full-length form and a shorter variant. Here, by studying the functional and structural relationship between the two SpaO forms in their native cellular environment, we define how and when they assemble within the injectisome. Employing quantitative injection assays in cultured cells, we define the shorter SpaO variant as an accessory structural piece that boosts effector delivery. These findings refine our understanding of injectisome assembly and function and provide mechanistic insight to inform future efforts to target T3SS-dependent pathogens through antivirulence strategies.
Journal Article