Try for free
DiscoverMobile appPricingFor schoolsHelpLogin
← Back to flashcardsQuick Flashcards

Microbiology Fundamentals Flashcards

An introductory lesson covering domains of life, cell types, key historical experiments, scientific method, human microbiota, nitrogen fixation, bacterial sh...

32 cards~11 min
Microbiology Fundamentals Flashcards — Qwi
1 / 32

All flashcards in this set

1What are the three domains of life?
Answer

Bacteria, Archaea, and Eukarya

These are the highest taxonomic ranks, grouping organisms based on fundamental cellular differences.
2There are {{three}} domains: Bacteria, Archaea, and Eukarya.
Answer

three

3There are four domains of life.
Answer

False

Only three domains are recognized: Bacteria, Archaea, and Eukarya.
4How do prokaryotic and eukaryotic cells differ?
Answer

Prokaryote → no membrane‑bound nucleus | Eukaryote → membrane‑bound nucleus

Prokaryotes lack a nucleus, while eukaryotes contain their genetic material within a nucleus and often have other organelles.
5Eukaryotic cells have a {{membrane‑bound nucleus}}.
Answer

membrane‑bound nucleus

6Prokaryotic cells have a membrane‑bound nucleus.
Answer

False

Prokaryotes lack a membrane‑bound nucleus; their DNA is in a nucleoid region.
7What did Francesco Redi demonstrate about worms on rotting meat?
Answer

They originated from fly eggs, not from the meat itself

Redi covered the meat with fine gauze to prevent flies from laying eggs; no worms appeared, disproving spontaneous generation.
8Redi covered meat with gauze and worms still appeared.
Answer

False

When the meat was covered with gauze, no worms appeared, showing they came from fly eggs.
9How did John Needham's and Lazzaro Spallanzani's experiments differ?
Answer

Needham → brief boiling, cork seal; Spallanzani → longer boiling, melted glass neck

Needham's short boil allowed microbes to survive; Spallanzani's longer boil and sealed neck prevented microbial growth, challenging spontaneous generation.
10Spallanzani sealed flasks by {{melting their glass necks}}.
Answer

melting their glass necks

11How did Pasteur's swan‑neck flask experiment disprove spontaneous generation?
Answer

The broth stayed sterile because microbes settled in the neck bends and couldn't reach the liquid.

When the flask was tipped, microbes entered the broth and grew, showing that air itself did not contain a 'vital force'.
12Microorganisms can reach the broth in a swan‑neck flask without tipping it.
Answer

False

The curved neck traps microbes, preventing them from reaching the broth unless the flask is tipped.
13What did John Tyndall discover about heat‑resistant microbial forms?
Answer

Some microorganisms exist in a heat‑resistant form later identified as endospores.

He realized that certain microbes survive boiling because they form resistant structures, explaining discrepancies in earlier experiments.
14These heat‑resistant forms are called {{endospores}}.
Answer

endospores

15What period is referred to as the Golden Age of Microbiology?
Answer

The era after Pasteur disproved spontaneous generation when microbiology blossomed.

During this time many key discoveries were made, including the acceptance of the Germ Theory of Disease.
16The Golden Age of Microbiology began before the 19th century.
Answer

False

It began after Pasteur's 1861 experiments, which are in the mid‑19th century.
17What are the four steps of the scientific method?
Answer

Observation → Question | Hypothesis → Experiment | Experiment → Data | Data → Conclusion

First observe and ask a question, then propose a hypothesis and test it, collect data, and finally draw a conclusion.
18The first step of the scientific method is {{making an observation}}.
Answer

making an observation

19The human body has roughly equal numbers of microbial and human cells.
Answer

True

Recent estimates suggest a ratio close to 1:1, not the previously cited 10:1.
20The microbial‑human cell ratio is closer to {{1:1}}.
Answer

1:1

21Name three ways the normal microbiota benefits human health.
Answer

Competes with pathogens, aids digestion, and trains the immune system

These functions prevent disease, break down otherwise indigestible foods, and help the immune system learn to distinguish friendly from harmful microbes.
22The normal microbiota have no effect on brain chemistry.
Answer

False

Animal studies suggest microbiota composition can influence brain chemistry and behavior.
23What is the process called where microbes convert atmospheric nitrogen into a usable form?
Answer

Nitrogen fixation

Rhizobia in legume root nodules perform this conversion, making nitrogen available to the plant.
24Beijerinck showed that rhizobia perform {{nitrogen fixation}}.
Answer

nitrogen fixation

25What are the main bacterial shapes?
Answer

Coccus → spherical | Bacillus → rod‑shaped | Vibrio → short curved rod

Other shapes include spirillum (curved rod) and spirochete (long spiral).
26A spherical bacterial cell is called a {{coccus}}.
Answer

coccus

27What arrangement results when cocci divide in one plane?
Answer

Chains

Dividing in a single plane produces linear chains of cells, as seen in Streptococcus species.
28Clusters form when cells divide in several planes at random.
Answer

True

Random division in multiple planes leads to grape‑like clusters, typical of Staphylococcus.
29How do bacterial and archaeal cell walls differ?
Answer

Bacteria → contain peptidoglycan | Archaea → lack peptidoglycan

Archaea may have pseudo‑peptidoglycan or other polymers, but not the classic peptidoglycan found in bacterial walls.
30Archaea have peptidoglycan in their cell walls.
Answer

False

Archaeal cell walls lack peptidoglycan, a hallmark of bacterial walls.
31What are the main differences among viruses, viroids, and prions?
Answer

Virus → nucleic acid + protein coat | Viroid → RNA only | Prion → protein only (misfolded)

Viruses have DNA or RNA inside a capsid, viroids are naked RNA molecules, and prions are misfolded proteins that induce misfolding of normal proteins.
32Viruses consist of nucleic acid surrounded by a {{protein coat}}.
Answer

protein coat

Domains of Life

The highest taxonomic ranks that group organisms based on fundamental cellular differences are the three domains of life: Bacteria, Archaea, and Eukarya. These domains represent the most inclusive classification level.

Key Distinction

Only three domains are recognized; any statement that there are four domains is false.

Prokaryotic vs. Eukaryotic Cells

Prokaryotic cells lack a membrane‑bound nucleus; their genetic material resides in a nucleoid region. In contrast, eukaryotic cells possess a membrane‑bound nucleus that houses their DNA and often contain additional organelles.

Defining Feature

The presence of a membrane‑bound nucleus is the defining characteristic of eukaryotes.

Historical Foundations of Microbiology

Early experiments challenged the idea of spontaneous generation.

Francesco Redi (1668)

Redi demonstrated that worms appearing on rotting meat originated from fly eggs. He covered the meat with fine gauze, preventing flies from laying eggs; no worms developed, disproving spontaneous generation.

John Needham (1745) vs. Lazzaro Spallanzani (1775)

Needham boiled broth briefly, sealed the flask with a cork, and observed microbial growth, supporting spontaneous generation. Spallanzani boiled the broth longer and sealed the flask by melting its glass neck, preventing microbial entry and showing that the earlier growth was due to insufficient sterilization.

Louis Pasteur (1859)

Pasteur used a swan‑neck flask: broth remained sterile because microbes settled in the curved neck bends and could not reach the liquid. When the flask was tipped, microbes entered the broth and grew, demonstrating that air itself does not contain a “vital force.”

John Tyndall (1861)

Tyndall discovered heat‑resistant microbial forms later identified as endospores. These structures allow certain microorganisms to survive boiling, explaining why some earlier experiments still yielded growth after sterilization.

Golden Age of Microbiology

The period after Pasteur’s 1861 experiments is referred to as the Golden Age of Microbiology. It began in the mid‑19th century, not before the 19th century, and saw rapid advances including the acceptance of the Germ Theory of Disease.

Scientific Method

The four steps of the scientific method are:

  1. Observation → Question
  2. Hypothesis → Experiment
  3. Experiment → Data
  4. Data → Conclusion

The first step is making an observation, which initiates the investigative process.

Human Microbiota

Recent estimates indicate that the human body contains roughly equal numbers of microbial and human cells, giving a ratio close to 1:1. The normal microbiota benefits health in three major ways:

  • Competes with pathogens, limiting their growth.
  • Aids digestion by breaking down otherwise indigestible substances.
  • Trains the immune system to distinguish friendly from harmful microbes.

Contrary to the statement that the normal microbiota has no effect on brain chemistry, animal studies suggest that microbial composition can influence brain chemistry and behavior.

Nitrogen Fixation

The process by which microbes convert atmospheric nitrogen (N₂) into a biologically usable form is called nitrogen fixation. Rhizobia bacteria in legume root nodules perform this conversion, making nitrogen available to the plant.

Bacterial Shapes and Arrangements

The main bacterial shapes are:

  • Coccus – spherical (e.g., Streptococcus).
  • Bacillus – rod‑shaped.
  • Vibrio – short curved rod.

When cocci divide in a single plane, they form chains. Random division in several planes produces grape‑like clusters, typical of Staphylococcus.

Cell Wall Differences

Bacterial cell walls contain peptidoglycan, a polymer that provides structural strength. Archaeal cell walls lack peptidoglycan; they may contain pseudo‑peptidoglycan or other polymers, but never the classic peptidoglycan found in bacteria.

Viruses, Viroids, and Prions

These three types of infectious agents differ in composition:

AgentComposition
VirusNucleic acid (DNA or RNA) surrounded by a protein coat
ViroidRNA only, no protein coat
PrionProtein only (misfolded)

Viruses consist of nucleic acid enclosed within a protein coat, which protects the genetic material and facilitates entry into host cells.