Bacterial Function: Motility and Resistance

Study Notes

Bacterial Function: Motility, Virulence Factors, and Antibiotic Resistance

Bacteria have a remarkable ability to adapt and thrive in various ecological niches.
This study focuses on key bacterial features and functions enabling adaptation.
Learning objectives include describing bacterial movement, explaining virulence factors, and understanding antibiotic resistance mechanisms.

Bacterial Motility: Flagella

Flagella are long, protein-based filaments.
Energy is required to maintain flagella.
Flagella enable bacteria to move in both liquids and on surfaces.
Various flagella arrangements exist in bacteria.

Bacterial Motility: Random Walk

Bacteria can exhibit random movement patterns.
Reversible flagella rotate counter-clockwise (CCW) or clockwise (CW).
Unidirectional flagella exhibit CW rotation for cell reorientation.
Peritrichous bacteria have flagella distributed over the entire cell surface. Flagella bundle and rotate in unison for forward movement, and rotate independently for tumbling.

Bacterial Motility: Chemotaxis

Chemotaxis is movement toward or away from a chemical signal.
Attractants are chemicals bacteria move toward.
Repellents are chemicals bacteria move away from.
Phototaxis is movement toward or away from light.
Bacteria use chemotaxis to find food sources and optimal environments

Bacterial Motility: Chemotaxis in Peritrichously Flagellated Bacteria

Random movement occurs when no attractant is present.
Directed movement occurs when an attractant is present, and increases the duration of the cell movement (run).

Biofilms

Biofilms are communities of bacteria on a surface.
A biofilm protects bacteria from death and biocides.
Biofilms are a cause of infection in medical devices.

Quorum Sensing

Quorum sensing is the ability of some bacterial species to sense the density of bacteria in their local area and adjust their behavior appropriately.
Bacteria communicate via signaling molecules.
Quorum sensing can occur between the same or different bacterial species, based on the density of signaling molecules in the local area.

Microbes and the Human Body

The human body contains 10 times more bacteria than human cells.
There are 10 times more viruses than bacteria in the human body, mostly in the gut.
Most bacteria are commensals (part of the normal flora).
Some bacteria are opportunistic pathogens, meaning they cause harm only in specific circumstances or locations.

Pathogens

Bacteria (and other microbes) that can cause disease are called pathogens.
Virulence is a pathogen's disease-causing potential.
Virulence factors are bacterial traits enabling pathogenicity.

Virulence Factors: Adhesion

Adhesion is a virulence factor allowing bacteria to attach to surfaces.
Some bacteria adhere to surfaces via capsules and pili.

Virulence Factors: Toxins

Toxins are molecules secreted by microorganisms that inhibit host cells, or kill host cells.
Endotoxins are released during bacterial cell division or lysis (rupturing), and affect their surroundings.
Exotoxins have a wider range of impact, including cells in locations other than microbial sites of infection. Exotoxins are secreted by the bacteria.

Endotoxins

Endotoxins are lipopolysaccharides (LPS) and lipoteichoic acid which are components of the bacterial cell wall.
Released during bacterial cell division or lysis, they cause harmful effects.

Exotoxins Example

Exotoxins, such as hemolysins, destroy red blood cells.
Different hemolysins cause varying levels of blood cell damage/ destruction in cultures.

AB Exotoxins Example

Botulinum and tetanus toxins are AB exotoxins.
AB toxins include a binding domain and a catalytic domain. The binding domain attaches the toxin to a target, while the catalytic domain carries out the toxin's damaging effects.

Antiobiotic Resistance

Intrinsic resistance is the ability of some bacteria to resist certain antibiotics through chromosomal DNA. This involves mechanisms such as lacking the target for the antibiotic or actively pumping the antibiotic out of the cell. Such resistance is often only effective against gram-positive bacteria.
Acquired resistance is shown through mutations or acquiring plasmids from other bacteria, which lead to high antibiotic resistance.

Horizontal Gene Transfer

Horizontal gene transfer is the method by which antibiotic resistance genes can be spread among different bacteria. This is achieved through transduction (phage), transformation (DNA), or conjugation (physical contact).

Description

This quiz explores bacterial motility, virulence factors, and antibiotic resistance mechanisms. Learn how flagella assist in bacterial movement and the various arrangements that exist. Additionally, discover the significance of random movement patterns in bacterial behavior.

Bacterial Function: Motility and Resistance

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Questions and Answers

What is the primary function of flagella in bacteria?

Bacteria can only move towards attractants through random walk mechanisms.

What is the process called that describes bacterial movement towards or away from chemicals?

The arrangement of flagella around a bacterium that allows it to move in different directions is called _____ flagellation.

Match the following components or processes related to bacterial movement:

What is the primary benefit of biofilms in bacterial communities?

Quorum sensing allows bacteria to sense the density of their species only.

What is the term for bacteria that normally coexist with the host and do not cause disease?

The degree to which a pathogen can cause disease is known as its ________.

Match the following virulence factors with their descriptions:

Which of the following is an example of a virulence factor?

Antimicrobial resistance can only be acquired through mutations.

What is the main difference between intrinsic and acquired antimicrobial resistance?