Microbiology: Microbes, Cell Structures, and Infectious Diseases

microorganisms/microbes

Organisms that are too small to be seen with the unaided eye, including bacteria, fungi, protozoa, microscopic algae, and viruses.

Robert Hooke

He examined cork with a crude microscope and reported that living things are composed of 'cells', marking the beginning of cell theory in 1665.

Anton van Leeuwenhoek

published his observations of 'Animalcules' in 1676, becoming the first person to view microbes.

Spontaneous generation

The idea that life arises from nonliving matter; a widely believed hypothesis about the origin of life until 160 years ago

Rudolf Virchow

proposed the hypothesis of biogenesis in 1855

hypothesis of biogenesis

living cells arise only from preexisting living cells.

Pasteur

He disproved spontaneous generation, demonstrating that microbes are present in nonliving matter and can be destroyed by heat in 1861.

aseptic techniques

Methods used to prevent microbial contamination and the spread of microbes.

germ theory of disease

The theory that microbes cause disease, established during the First Golden Age of Microbiology.

Koch's postulates

Criteria established to show that specific diseases are caused by specific microbes.

immunity

Protection from disease, which can be achieved through vaccination or recovery from disease.

chemotherapy

The treatment of disease with chemicals, including synthetic drugs and antibiotics.

Penicillin

first antibiotic discovered

The Third Golden Age of Microbiology.

current era of microbiology referred to as

bacteriology

The study of bacteria.

mycology

The study of fungi

parasitology

The study of protozoa and parasitic worms

virology

The study of viruses.

focus of microbial genetics

How microbes inherit traits.

The relationship between microorganisms and their environment.

What does microbial ecology examine?

immunology

study of Immunity

How DNA directs protein synthesis.

What does molecular biology investigate?

genomics

involves examining an organism's genes, providing tools for classifying microorganisms.

beneficial and play crucial roles in various life processes

Why are microbes essential for life?

Microorganisms

What is the basis of the aquatic food web?

decomposition

How do microorganisms recycle chemical elements?

convert N2 into useable NH3

What unique ability do bacteria have regarding atmospheric nitrogen?

How do microorganisms contribute to human welfare?

provide models for research, chemical products, fermented foods, and are used in sewage treatment and bioremediation.

biotechnology

use of biological processes, especially involving microbes, for practical applications like producing foods and chemicals.

recombinant DNA technology

enables bacteria and fungi to produce substances they naturally could not.

products of recombinant DNA technology?

insulin, vaccines, and cellulose used in manufacturing.

5%

What percentage of microbes are pathogenic?

pathogen

microbe that can cause disease and carries out part of its life cycle in an infected host.

infectious disease

caused by pathogens invading a susceptible host.

It allows humans to prevent disease and understand the causes and transmission to prevent epidemics.

Why is knowledge of pathogenic microorganisms important?

emerging infectious diseases (EIDs)

new diseases or diseases that are increasing in incidence due to factors like mutation and increased human exposure.

examples of antibiotic-resistant infections

Methicillin-resistant Staphylococcus aureus (MRSA) and multi-drug-resistant tuberculosis (MDR-TB).

biofilm

community of microbes where cells stick to each other and usually to a surface, often protected by a slime-like outer layer.

example of biofilm

The plaque on teeth

examples of emerging infectious diseases

Zika virus disease, Middle East respiratory syndrome (MERS), COVID-19, and Ebola hemorrhagic fever (EHF).

contributing factors of emergence of infectious diseases

mutation of existing organisms, spread to new geographic locations, and increased human exposure to pathogens.

Lab strains lack anti-antibodies to spread outside of lab

How do lab strains of microbes differ from those in nature?

Microbes from the mammal may be suited for the human if they have adapted to other mammals.

What happens when a mammal bites a human?

used to produce fermented foods

What role do microorganisms play in food production?

used in sewage treatment and bioremediation.

How do microorganisms assist in environmental processes?

rocks, pipes, teeth, capsular material, plastic, and medical implants.

Where can biofilms grow?

can cause infections and are often resistant to antibiotics.

major characteristic of biofilms

resistance

ability of the body to ward off disease.

Disease

What happens when a pathogen overcomes the host's resistance?

resistance factors of the human body

skin, stomach acid, natural antimicrobial chemicals (e.g., interferon), and normal microbiota.

normal microbiota

microbes normally present in and on a healthy human body.

newborns

When do humans acquire normal microbiota?

Over 40 trillion

How many bacterial cells live on or in the average adult human body?

microbiome

all the microorganisms in an environment.

benefits of the human microbiome

maintain good health, prevents growth of pathogenic microbes, and may help train the immune system.

to determine the makeup of typical microbiota of various areas of the body and understand the relationship between changes in microbiome and human diseases.

goal of The Human Microbiome Project

role microbes play in different ecosystems.

What does the National Microbiome Initiative explore?

Carolus Linnaeus (1735)

Who created the system of scientific nomenclature?

genus name (capitalized) and species name (lowercase).

What are the two parts of a scientific name?

italicized/underlined

How should scientific names be formatted?

honors the discoverer (Escherich) and describes the bacterium's habitat in the large intestine (colon)

What does Escherichia coli honor?

S clustered (staphylo-) spherical (coccus) cells and gold-colored (aureus) colonies

What does Staphylococcus aureus describe?

first letter of the genus and the full specific epithet, still italicized/underlined.

How can scientific names be abbreviated after the first use?

What are the eight major groups of microorganisms?

Archaea, Bacteria, Eukarya, Fungi, Protozoa, Multicellular Animal Parasites, Algae, and Nonliving entities like Viruses and Prions.

micrometers (μm) and nanometers (nm).

What units are used to measure microorganisms?

1 µm = 0.000001 meters or 1 meter = 1,000,000 µm

What is the conversion between micrometers and meters?

1 nm = 0.000000001 meters or 1 meter = 1,000,000,000 nm

What is the conversion between nanometers and meters?

1 nm = 0.001 µm or 1 µm = 1,000 nm

What is the conversion between nanometers and micrometers?

light microscopy

Microscopes that use visible light to observe specimens.

types of light microscopy

Compound light microscopy, darkfield microscopy, phase-contrast microscopy, differential interference contrast (DIC) microscopy, fluorescence microscopy, and confocal microscopy.

ocular lens

magnifies the image from the objective lens.

Total magnification

objective lens magnification × ocular lens magnification

4X, 10X, 40X, and 100X.

What are the common magnifications of objective lenses used in light microscopy?

Approximately 0.25 µm.

What is the resolving power of a compound light microscope?

resolution

The ability to distinguish between two points.

Immersion oil has a refractive index similar to glass, which reduces light refraction and increases resolution.

Why is immersion oil used in microscopy?

Most light is refracted and lost, reducing the quality of the image.

What happens to light without immersion oil in microscopy?

1.51

What is the refractive index of glass/immersion oil

enhances contrast and emphasizes certain structures in microorganisms.

Why is staining important in microscopy?

smear

A thin film of material containing microorganisms spread over a glass slide.

To attach them to the slide, kill organisms, and preserve structures for observation.

What is the purpose of fixing microbes to a slide?

Attaching specimens to the slide using the flame from a Bunsen burner.

What is the process of heat fixing in microbiology?

Avoid overheating, as it can destroy bacteria.

What precautions should be taken during heat fixing?

To focus light onto the specimen.

What is the role of the condenser lenses in microscopy?

iris diaphragm

To control the amount of light reaching the specimen.

little contrast with their surroundings.

What is the main challenge when observing unstained specimens?

Creating a smear and fixing the microbes to the glass slide.

What is the first step before staining microbes?

It attaches them to the slide, kills them, and preserves their structures.

What does fixing microbes accomplish?

body tube

It houses a series of lenses for magnification.

illuminator

To provide a source of illumination for the specimen.

Simple stain, differential stain, and special stain.

What are the three common staining techniques used in microbiology?

simple stain

highlights the entire microorganism to visualize cell shapes and structures using a single dye.

differential stain

To distinguish between different bacterial species based on structural differences.

special stain

To color specific structures such as flagella and capsules.

primary stain

The first dye used to color a microbe.

counterstain

The second dye used after a wash step in the staining process.

mordant

substance used to set or bind the dye and intensify staining.

A single basic dye that binds to negatively charged areas of bacteria.

What type of dye is typically used in simple stains?

Crystal violet, safranin, and methylene blue.

What are some typical dyes used in simple staining?

gram stain

classifies bacteria into gram-positive or gram-negative groups based on their cell wall structure.