42 Questions
What characteristic do bacteria lack?
Membranous organelles
What is unique about the growth rate of bacteria?
Some bacteria grow rapidly, while others grow slowly
What is a characteristic of opportunistic pathogens?
They cause disease only in immunocompromised individuals
What is a characteristic of commensal bacteria?
They reside on or inside the host without harming it
Who is credited with the discovery of microorganisms?
Antoni van Leeuwenhoek
What is the main difference between true pathogens and opportunistic pathogens?
True pathogens cause disease in healthy individuals, while opportunistic pathogens cause disease in immunocompromised individuals
What is the function of ribosomes in bacterial cells?
To manufacture proteins
What are the two main subunits of ribosomes?
30S and 50S
What is the role of the genetic code in ribosomes?
To determine the sequence of amino acids
What are the two main applications of ribosomes?
Therapy and phylogeny
What is the layer outside the cytoplasmic membrane in a bacterial cell?
Cell wall
What is the function of the bacterial envelope?
To maintain cell shape and provide support
What is the primary component of the bacterial cell wall?
Peptidoglycan
What is the function of membrane-associated proteins in the bacterial envelope?
To facilitate transport and signaling
What is the target of some antibiotics, according to Poehlsgaard and Douthwaite?
Bacterial ribosomes
What is the main characteristic that distinguishes prokaryotes from eukaryotes?
Lack of membranous organelles
Which of the following structures is present in all bacteria?
Nucleoid (DNA)
What is the function of the cytoplasm in a bacterial cell?
To synthesize proteins
What is the exception to the complex and rigid cell wall in bacteria?
Mycoplasma
What is the term for the region where the DNA is located in a bacterial cell?
Nucleoid
What are the three main components of the cytoplasm in a bacterial cell?
Macromolecules, small molecules, and water
What is the function of the plasma membrane in a bacterial cell?
To regulate the movement of solutes
What is the term for the protective layer outside the plasma membrane in some bacteria?
Capsule
What is the term for the dormant, highly resistant structure that some bacteria can form?
Endospore
What is the primary function of flagella in bacteria?
Locomotion or bacterial motility
What is the main function of pili/fimbriae in bacteria?
Adhesion to host tissues
Which type of bacteria produce endospores?
Gram-positive bacteria
What is the purpose of endospores?
To ensure survival during adverse environmental conditions
What is the result of spore germination?
The formation of vegetative bacilli
What is the characteristic of endospores?
They are highly resistant to all of the above
What is the function of flagella in relation to bacterial movement?
It enables locomotion or bacterial motility
What is the characteristic of pili/fimbriae?
They are fine, straight, hair-like appendages
What is the purpose of bacterial toxins synthesized by vegetative bacilli?
To cause harm to the host
What is the origin of a bacterial colony in solid media?
A single bacterium
What is the term for a single bacterium that can give rise to a colony?
Colony Forming Unit (CFU)
What can affect the morphology of a bacterial colony?
The growth medium used
What is the process by which bacteria replicate?
Binary fission
What is an essential environmental factor required for bacterial growth?
Nutrients
What is the optimal pH range for most pathogenic bacteria?
7.2-7.4
What can cause different colony morphologies in the same bacterial species?
Different growth media
What is a characteristic of bacterial growth?
It requires specific environmental factors
What determines the shape of a bacterial colony?
The growth medium used
Study Notes
Bacteriology Overview
- Bacteria are unicellular organisms that lack membranous organelles and a true nucleus.
- They are small in size, large in number, and have evolved to survive in various ecological niches.
- Some bacteria grow rapidly, while others grow slowly, and they require minimal to fastidious nutrients to grow.
Bacteria in Numbers
- There are approximately 1.3 x 10^29 bacteria in oceans, which is 100 million times more cells than stars in the visible universe.
- There are more microbes in a teaspoon of soil than there are people on earth.
- Human adults excrete their own weight in fecal bacteria every year.
- There are approximately 1 x 10^11 bacteria in 1g of dental plaque, which is the same number as humans who have ever lived.
- Approximately 16,000,000 people worldwide die from infectious diseases every year.
Types of Bacteria
- Bacteria can be true pathogens, opportunistic pathogens, or commensals.
- True pathogens can cause disease in healthy immunocompetent individuals.
- Opportunistic pathogens are organisms that usually do not cause disease but can induce an infectious process in weakened individuals.
- Commensal bacteria reside on the surface or internal mucosae of the host without harming it, often forming a mutualistic relationship.
Bacterial Cell Structure
- Prokaryotes lack membranous organelles and have a unicellular structure.
- All bacteria have cytoplasm, ribosomes, a nucleoid (DNA), a plasma membrane, and a complex and rigid cell wall (except for one exception).
- Some bacteria have additional features such as capsules, flagella, pili/fimbriae, and plasmids, and some can produce endospores.
Cytoplasm
- Cytoplasm is a jelly-like aqueous solution (cytosol) containing three main components: macromolecules (proteins, mRNA, tRNA), small molecules (precursors of macromolecules, metabolites, ATP, etc.), and bacterial cell structures.
Ribosomes
- Ribosomes are the cellular protein factory, composed of proteins and rRNA.
- They consist of two subunits: large (50S) and small (30S).
- Ribosomes have a conserved genetic code and are used in therapy and phylogeny.
Bacterial Envelope
- The bacterial envelope consists of the cytoplasmic or plasma membrane, membrane-associated proteins, a cell wall (peptidoglycan layer), and other components.
Flagella
- Flagella are anchored to the bacterial cell envelope, are multi-protein structures, and have varying numbers and positions between bacteria.
- They function in locomotion or bacterial motility.
Pili/Fimbriae
- Pili/fimbriae are fine, straight, hair-like appendages attached to the cell wall, known as "adhesins".
- They are most common on Gram-negative bacteria and function in adhesion to host tissues and contributing to antigenicity.
Endospores
- Endospores are the cryptobiotic state of dormancy, the most durable type of cell found in nature, and are produced by Gram-positive bacteria.
- They function in ensuring survival during adverse environmental conditions and are dormant, highly resistant bodies.
Bacterial Cell and Colony Morphology
- A bacterial colony is a macroscopic aggregate of bacteria in solid media, originated from a single bacterium, and is theoretically a Colony Forming Unit (CFU) = 1 bacterium.
- Colonies may look different during time and depending on the growth medium used.
Bacterial Growth and Metabolism
- Bacterial growth occurs through binary fission, where one mother cell results in two daughter cells.
- Specific environmental factors are required for bacterial growth, including nutrients, pH, ionic strength and osmotic pressure, and light.
An overview of bacteriology, covering the basic concepts and characteristics of bacteria, including their structure, growth, and habitats.
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