Movement of mucus in the respiratory tract
The mucous membrane lining our respiratory system has evolved (or, according to creationists, been intelligently [sic] designed) to keep our respiratory system clean as we breathe in air containing particles of dirt, dust, pollen and bacteria. It does this by secreting mucus that traps the particles, then ciliated cells on the surface sweep them towards our pharynx to be swallowed and disposed of in our digestive system where the proteins in the mucous are recycled.
Other body cavities are lined by a mucous membrane that serves to protect and keep the cavity moist and lubricated.
But, in one of those research papers that creationists have to avoid reading, a team of researchers from Penn State University, have shown how bacteria have evolved (or been intelligently [sic] designed, according to creationists) to exploit the mucous, the better to infect us and make us sick, and the thicker the mucus, the better it is for these would-be pathogens.
Infections by bacteria, known medically as opportunist infections, especially in the nasal sinuses and lungs, are a frequent complication of viral infections such as a common cold or influenza. These opportunist infections can be more dangerous than the virus infections that facilitate them.
The team showed that bacteria find it easier to swim, swarm and form colonies in thick mucus than in thin, watery mucus and that this swarming probably helps protect them from the antibacterial enzymes in the mucus.
Their research is explained in a Penn State news release:
Sniffles, snorts and blows of runny noses are the hallmarks of cold and flu season — and that increase in mucus is exactly what bacteria use to mount a coordinated attack on the immune system, according to a new study from researchers at Penn State. The team found that the thicker the mucus, the better the bacteria are able to swarm. The findings could have implications for treatments that reduce the ability of bacteria to spread.The dismal news for creationists continues unabated in the published paper in the journal PNAS Nexus:
The study, recently published in the journal PNAS Nexus, demonstrates how bacteria use mucus to enhance their ability to self-organize and possibly drive infection. The experiments, performed using synthetic pig stomach mucus, natural cow cervical mucus and a water-soluble polymer compound called polyvidone, revealed that bacteria coordinate movement better in thick mucus than in watery substances.
The findings provide insight into how bacteria colonize mucus and mucosal surfaces, researchers said. The findings also show how mucus enhances bacterial collective motion, or swarming, which may increase antibiotic resistance of bacterial colonies.
To the best of our knowledge, our study is the first demonstration of bacteria collectively swimming in mucus. We have shown that mucus, unlike liquids of similar consistency, enhances the collective behavior.
Professor Igor Aronson, Corresponding author
Huck Chair Professor of Biomedical Engineering, of Chemistry and of Mathematics
Department of Biomedical Engineering
Pennsylvania State University, University Park, PA, USA.
Mucus is essential for many biological functions, explained Aronson. It lines the surfaces of cells and tissues and protects against pathogens such as bacteria, fungi and viruses. But it is also the host material for bacteria-born infections, including sexually transmitted and gastric diseases. A better understanding of how bacteria swarm in mucus could pave the way for new strategies to combat infections and the growing problem of antibiotic resistance, according to Aronson.
Mucus is a notoriously challenging substance to study because it exhibits both liquid-like and solid-like properties, Aronson explained. Liquids are typically described by their level of viscosity, how thick or thin the liquid is, and solids are described by their elasticity, how much force it can take before breaking. Mucus, a viscoelastic fluid, behaves as both a liquid and solid.Our findings demonstrate how mucus consistency affects random motion of individual bacteria and influences their transition to coordinated, collective motion of large bacterial groups. There are studies demonstrating that collective motion or swarming of bacteria enhances the ability of bacterial colonies to fend off the effect of antibiotics. The onset of collective behavior studied in our work is directly related to swarming.
Professor Igor Aronson
To better understand how mucus becomes infected, the team used microscopic imaging techniques to observe the collective motion of the concentrated bacteria Bacillus subtilis in synthetic pig stomach mucus and natural cow cervical mucus. They compared those results with observations of Bacillus subtilis moving in a water-soluble polymer polyvidone at a wide range of concentrations, from high to low levels of polyvidone. The researchers also compared their experimental results to a computational model for bacterial collective motion in viscoelastic fluids like mucus.
The team found that the consistency of mucus profoundly affects the collective behavior of bacteria. The results indicated that the thicker the mucus, the more likely the bacteria would exhibit collective movement, forming a coordinated swarm.
The left side shows computational modeling results of model bacteria undergoing polymer stress, or thicker mucus. The right side is not undergoing polymer stress.Credit: Provided by Igor Aronson. All Rights Reserved.
Aronson explained that the team expects human mucus to exhibit similar physical properties, meaning their findings are also relevant for human health.We were able to show how the viscoelasticity in mucus enhances bacterial organization, which in turn leads to coherently moving bacterial groups that cause infection. Our results reveal that the levels of elasticity and viscosity in mucus are a main driver in how bacterial communities organize themselves, which can provide insight into how we can control and prevent bacterial invasion in mucus.
Professor Igor AronsonThe onset of the collective motion of bacteria and their interaction with mucus should be the same as in cow, pig or human mucus since these substances have similar mechanical properties. Our results have implications for human and animal health. We’re showing that mucus viscoelasticity can enhance large-scale collective motion of bacteria, which may accelerate how quickly bacteria penetrate mucus protective barrier and infect internal tissues.
Professor Igor Aronson
To make matters worse for creationists, there is that bacterial flagellum, that they claim Michael J Behe showed is proof of their magic designer god's existence. Here we see how it makes it easier for bacteria to make us sick by using the mucus this same putative intelligent [sic] designer designed to protect us from those same bacteria it designed to make us sick.Abstract
Bacteria form human and animal microbiota. They are the leading causes of many infections and constitute an important class of active matter. Concentrated bacterial suspensions exhibit large-scale turbulent-like locomotion and swarming. While the collective behavior of bacteria in Newtonian fluids is relatively well understood, many fundamental questions remain open for complex fluids. Here, we report on the collective bacterial motion in a representative biological non-Newtonian viscoelastic environment exemplified by mucus. Experiments are performed with synthetic porcine gastric mucus, natural cow cervical mucus, and a Newtonian-like polymer solution. We have found that an increase in mucin concentration and, correspondingly, an increase in the suspension’s elasticity monotonously increases the length scale of collective bacterial locomotion. On the contrary, this length remains practically unchanged in Newtonian polymer solution in a wide range of concentrations. The experimental observations are supported by computational modeling. Our results provide insight into how viscoelasticity affects the spatiotemporal organization of bacterial active matter. They also expand our understanding of bacterial colonization of mucosal surfaces and the onset of antibiotic resistance due to swarming.
Significance Statement
Mucus, a gel-like viscoelastic substance, is essential for many biological functions. Mucus lines the surfaces of cells and tissues. It is permeable to oxygen and nutrients and protects against pathogens such as bacteria, fungi, and viruses. Understanding bacterial motility in mucus-like fluids provides insights into bacteria-born infections, including sexually transmitted and gastric diseases. This work demonstrates that mucus viscoelasticity enhances bacterial organization, leading to the emergence of coherently moving bacterial groups. The results shed light on how viscoelasticity controls the spatiotemporal organization of bacterial communities and provide insight into controlling and preventing bacterial invasion of mucosal surfaces.
Introduction
Bacteria are the most abundant species on Earth. They compose human and animal microbiota and are sources of many infectious diseases (1). Suspension of motile bacteria is an important class of active matter: nonequilibrium systems transducing energy from the environment into mechanical motion. Concentrated bacterial suspensions often exhibit large-scale turbulent-like motion (so-called bacterial turbulence) (2, 3). While significant knowledge is accumulated on the collective dynamics of bacterial suspensions in Newtonian liquids, complex fluids are mostly “terra incognita” (4). Bacterial habitats are not limited to Newtonian fluids such as water. Bacteria thrive in non-Newtonian environments (4) exemplified by lyotropic liquid crystals (5, 6), mucus (7, 8), DNA solutions (9, 10), blood (11), saliva (12), biofilm matrices (13), or mammalian extracellular matrices (14). Unlike the simple viscous response in a Newtonian liquid, the non-Newtonian rheology of biological viscoelastic fluid can drastically alter the bacterial collective motion (15, 16)…
Instant flow patterns of bacterial collective motion in mucus and PVP360. A) Schematics of the experimental setup. A free-standing film containing bacterial suspension in mucus is stretched between 4 movable wires. B) A schematic representation of motile bacteria (blue bodies with flagella) swimming in tunnels formed by mucin polymers (black tubes). The blue (brighter in grey-scale image representation) arrow indicates the swimming direction of mobile bacteria. The trapped bacteria are shown in red. C–E) Select frames illustrating instant flow patterns at the bottom of the film for different concentrations of mucin/PVP360; black arrows depict the direction and magnitude of bacterial flow, and colors show the vorticity w of bacterial flow. C) Instant flow pattern in 50 mg/mL mucin solution. D) Instant flow pattern in 200 mg/mL mucin solution. E) Instant flow pattern in 125 mg/mL PVP360 solution. The scale bar in all figures is 80 μm.
Wentian Liao, Igor S Aranson
Viscoelasticity enhances collective motion of bacteria
PNAS Nexus, Volume 2, Issue 9, September 2023, pgad291, https://doi.org/10.1093/pnasnexus/pgad291
Copyright: © 2023 The authors.
Published by Oxford University Press on behalf of the National Academy of Sciences. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
If this was really the work of a designer, that designer could only be regarded as stupidly incompetent or intelligently malevolent, but for reasons which can only be guessed at, creationists would rather we thought of the god they purport to worship as one or the other than have us believing this is all the result of evolution by natural selection in which neither magic nor supernatural intervention were involved.
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