Microbiology Quiz: Bacteria and Pathogens

Deeply Branching Bacteria

• Aquifex is an example of deeply branching bacteria, which are thought to be among the earliest forms of bacteria.
• Aquifex is a hyperthermophile, meaning it thrives in extremely high temperatures.

Phototrophic Bacteria

• Cyanobacteria are phototrophic bacteria known for their ability to perform oxygenic photosynthesis.

Low G+C Gram-Positive Bacteria

• Low G+C Gram-Positive Bacteria have a lower guanine and cytosine content in their DNA.
• Staphylococcus is a common genus of low G+C Gram-Positive bacteria known for causing skin infections.
• Mycoplasmas are low G+C Gram-positive bacteria with a unique pleomorphic (variable) shape. Mycoplasmas lack a cell wall.
• Bacillus and Clostridium are examples of low G+C Gram-Positive bacteria that form endospores. Endospores allow these bacteria to survive harsh conditions.

High G+C Gram-Positive Bacteria

• High G+C Gram-Positive Bacteria have a higher guanine and cytosine content in their DNA.
• Mycobacterium is a genus of high G+C Gram-Positive bacteria that have a unique waxy cell wall. Mycobacterium can cause tuberculosis.
• Streptomyces is a genus of high G+C Gram-Positive bacteria known for producing a variety of antibiotics.

Gram Negative Proteobacteria

• Proteobacteria are a diverse group of Gram-negative Bacteria.
• Alphaproteobacteria are a class of Proteobacteria that include Rhizobium, nitrogen-fixing bacteria, Agrobacterium, which can cause crown galls in plants, and Nitrobacter, a bacteria involved in nitrification.
• Betaproteobacteria include Bordetella, which causes whooping cough.
• Gamaproteobacteria include Pseudomonas, bacteria that can cause infections in plants and animals.
• Epislonproteobacteria include Helicobacter, a bacteria that can cause stomach ulcers.

Other Gram Negative Bacteria

• Chlamydias are obligate intracellular bacteria that can cause sexually transmitted infections.

Spirochetes

• Borrelia is a genus of Spirochetes, which are spiral-shaped bacteria. Borrelia burgdorferi is the cause of Lyme disease.

Archaea

• Archaea are prokaryotic organisms that have unique features that distinguish them from Bacteria.
• Archaea have different cell wall components, unique membrane lipids, and distinct ribosomal RNA sequences.
• Unlike bacteria, archaea have a different type of phospholipid in their cell membrane.

Major Groups of Archaea

• Thermophiles are archaea that thrive in extremely high temperatures. Thermococcus is an example of a thermophile.
• Methanogens are archaea that produce methane gas as a byproduct of their metabolism.
• Halophiles are archaea that live in extremely salty environments. Halobacterium salinarium is an example of a halophile.

Protozoa

• Protozoa are single-celled eukaryotic organisms that are diverse in their forms and lifestyles.
• Some protozoa are free-living, while others are parasitic.

Major Groups of Protozoa

• Diplomonadida are protozoa that have two nuclei. Giardia is an example of a Diplomonadid.
• Euglenozoa are protozoa that have flagella for movement. Euglena is an example of an Euglenozoa. Kinetoplastids, found in Euglenozoa, are protozoa that have a single mitochondrion containing a distinct region of DNA (kinetoplast). Trypanosoma, the cause of African sleeping sickness, is an example of a Kinetoplastid.
• Alveolates are protozoa that have membrane-bound sacs called alveoli. Dinoflagellates are an example of an Alveolate, and they are known for their bioluminescence. Cilliates, another type of Alveolate, have hair-like structures called cilia for movement. Apicomplexans are parasites that have a complex life cycle. Plasmodium, the cause of malaria, is an example of an Apicomplexan.
• Rhizaria are protozoa that have a unique shell called a test. Radiolaria are an example of a Rhizaria.
• Amoebozoa are protozoa that move by extending pseudopods. Naegleria fowleri, brain-eating amoeba, is an example of an Amoebozoa. Amoebozoa also include slime molds.

Fungi

• Fungi are eukaryotic organisms that are heterotrophic, obtaining nutrients by absorbing organic matter.
• Fungi are important decomposers.

Major Groups of Fungi

• Zygomycota are fungi that form a thick-walled zygospore during sexual reproduction.
• Ascomycota are fungi that form a sac-like structure (ascus) during sexual reproduction.
• Basidiomycota are fungi that form a club-shaped structure (basidium) during sexual reproduction.
• Deuteromycetes are fungi that do not produce spores sexually.

Lichens

• Lichens are a symbiotic association between a fungus and an alga.

Algae

• Algae are eukaryotic organisms that are photosynthetic but lack true roots, stems, and leaves.

Major Groups of Algae

• Chlorophyta are green algae that have cellulose in their cell walls.
• Rhodophyta are red algae, which have agar, a gel-like substance, in their cell walls.
• Phaeophyta are brown algae that have a cellulose cell wall.
• Chrysophyta include golden algae, yellow-green algae, and diatoms.

Water molds (Oomycetes)

• Water molds are not true fungi but are closely related to algae.
• Water molds use cellulose in their cell walls and produce motile spores.
• Phytophtora is a water mold that causes diseases in plants, including potato blight.

Animals

• Animals are multicellular eukaryotic organisms that are heterotrophic.

Arthropods

• Arthropods are invertebrates with segmented bodies, jointed appendages, and an exoskeleton.
• Arachnids include spiders, ticks, and scorpions. Ticks are arachnids that can transmit diseases.
• Insects include mosquitoes, fleas, flies, and lice that can transmit diseases to humans.

Nematodes, Annelids, Platyhelminths

• Nematodes are roundworms that can cause parasitic infections.
• Annelids are segmented worms.
• Platyhelminths are flatworms that can cause parasitic infections.

Helminths

• Helminths are parasitic worms that can infect humans.

Characteristics of Viruses

• Viruses are non-cellular infectious agents that require a host cell to replicate.
• Viruses are typically smaller than bacteria.

Virus Structure

• Viruses have a protein capsid that encloses a nucleic acid genome.
• Some viruses have an outer envelope derived from their host's cell membrane.
• Viral genomes can be DNA or RNA.

Virus Life Cycle Steps

• The lytic cycle is a viral replication pathway that results in the lysis (bursting) of the host cell.
• The lysogenic cycle is a viral replication pathway in which the viral genome integrates into the host cell's genome, replicating along with the host cell.

RNA Viruses, DNA Viruses, Retroviruses

• RNA viruses have an RNA genome.
• DNA viruses have a DNA genome.
• Retroviruses are RNA viruses that use an enzyme called reverse transcriptase to convert their RNA genome into DNA, which can then integrate into the host cell's genome. HIV, the virus that causes AIDS, is a Retrovirus.

Cancer: Protoncogenes (Oncogenes) and Tumor Suppressor Genes

• Protoncogenes are normal genes that regulate cell growth and division.
• Oncogenes are mutated versions of protoncogenes that can lead to uncontrolled cell growth, resulting in cancer.
• Tumor suppressor genes are genes that normally inhibit cell growth and division. Mutations in tumor suppressor genes can lead to cancer.

Benign vs Malignant Tumor, Metastasis, and Angiogenesis

• Benign tumors are non-cancerous growths that do not invade surrounding tissues.
• Malignant tumors are cancerous growths that invade surrounding tissues and can spread to other parts of the body.
• Metastasis is the spread of cancer cells from the primary tumor to other parts of the body.
• Angiogenesis is the formation of new blood vessels, which can supply nutrients and oxygen to a growing tumor.

Culturing Viruses

• Viruses can be cultured in living cells or organisms.

Viroids

• Viroids are infectious agents that are smaller than viruses and consist only of a short strand of RNA without a protein coat.
• Viroids cause diseases in plants.

Prions

• Prions are infectious agents consisting only of misfolded proteins.
• Prions can cause diseases in animals and humans.
• Prions can convert normal proteins into misfolded prions, leading to the formation of aggregates.
• Prions are resistant to heat, chemicals, and radiation.

Spongioform Encephalopathies

• Spongioform encephalopathies are neurodegenerative diseases caused by prions.
• They are characterized by the formation of holes (spongiform changes) in the brain tissue.
• Spongioform encephalopathies include mad cow disease (Bovine Spongiform Encephalopathy), Chronic Wasting Disease, scrapie, and kuru.

Symbiosis

• Symbiosis is a close and long-term interaction between two different species.
• Mutualism is a symbiotic relationship where both species benefit.
• Commensalism is a symbiotic relationship where one species benefits, and the other species is neither harmed nor helped.
• Parasitism is a symbiotic relationship where one species benefits at the expense of the other species.

Human Microbiome

• The human microbiome is the collection of microorganisms that live in and on the human body.
• Resident microbiota are microorganisms that permanently live on the human body.
• Transient microbiota are microorganisms that temporarily live on the human body.

Reservoirs

• Reservoirs are sources of infection.
• Animal reservoirs are animals that harbor pathogens that can infect humans.
• Human reservoirs are people who harbor pathogens that can infect other people.
• Nonliving reservoirs are environmental sources of pathogens, such as soil, water, and food.

Carriers

• Carriers are people who harbor a pathogen without showing symptoms of illness.
• Asymptomatic carriers are people who show no symptoms, but they can spread the pathogen.

Zoonoses

• Zoonoses are diseases that can be transmitted from animals to humans.

Opportunistic Pathogens

• Opportunistic pathogens are microorganisms that are normally harmless but can cause disease under certain circumstances.

Portals of Entry

• Portals of entry are the routes by which pathogens enter the host's body.
• Mucous membranes are common portals of entry, including the respiratory tract, gastrointestinal tract, and genitourinary tract.

Role of Adhesion

• Adhesion is the process by which pathogens attach to host cells.
• Adhesion factors are molecules on the surface of pathogens that help them attach to host cells.

Stages of Infectious Disease

• Incubation period is the time between infection and the appearance of symptoms.
• Prodromal period is a period of mild symptoms.
• Illness is the period of most severe symptoms.
• Decline is the period when symptoms start to subside.
• Convalescence is the period of recovery.

Pathogenicity and Virulence

• Pathogenicity is the ability of a pathogen to cause disease.
• Virulence is the degree of pathogenicity.

Virulence Factors

• Virulence factors are traits that contribute to the pathogenicity of a microorganism.

Modes of Disease Transmission

• Contact transmission is the spread of pathogens through direct contact with an infected person or animal, indirect contact with an object contaminated with a pathogen, or through droplets released from an infected person.
• Vehicle transmission is the spread of pathogens through contaminated objects, such as water, food, or air.
• Vector transmission is the spread of pathogens through living organisms, such as insects or arthropods.

Incubation Period

• Incubation period is the time between infection and the onset of symptoms.

Portals of Exit

• Portals of exit are the routes by which pathogens leave the infected host.

Sign vs Symptom

• Sign is an objective indication of a disease that is observed by a health care provider.
• Symptom is a subjective indication of a disease that is experienced by the patient.

Etiology

• Etiology is the cause of a disease.

Koch's Postulates

• Koch's postulates are a set of criteria used to establish a causal relationship between a microorganism and a disease.
• The four postulates are:
  • The microorganism must be found in all cases of the disease.
  • The microorganism must be isolated from the diseased host and grown in pure culture.
  • The microorganism from the pure culture must cause the disease when inoculated into a healthy host.
  • The microorganism must be isolated from the inoculated, diseased host and identified as the original microorganism.

Disease Transmission

• Biological vector are vectors that are required for a pathogen to complete its life cycle.
• Mechanical vector are vectors that passively spread pathogens through contact with contaminated surfaces.
• Airborne transmission is the spread of pathogens through the air.
• Waterborne transmission is the spread of pathogens through contaminated water.
• Foodborne transmission is the spread of pathogens through contaminated food.
• Bodily fluid transmission is the spread of pathogens through blood, urine, feces, saliva, and other bodily fluids.
• Direct contact transmission involves physical contact between an infected person and a susceptible person.
• Indirect contact transmission involves contact with an object contaminated with a pathogen.
• Droplet transmission is a type of direct contact transmission involving the spread of droplets from an infected person.

Epidemiology

• Epidemiology is the study of the occurrence, distribution, and determinants of health and disease in populations.
• Incidence is the number of new cases within a given population over a given time.
• Prevalence is the total number of cases within a given population at a given time.

Healthcare Associated Infections (Nosocomial Infections)

• Healthcare associated infections (nosocomial infections) are infections acquired in a hospital or other healthcare setting.
• Exogenous infections: are caused by pathogens acquired from the healthcare environment.
• Endogenous infections: are caused by pathogens from the patient's own normal microbiota.
• Iatrogenic infections: are infections caused by medical procedures.
• Superinfections: are infections that occur on top of existing infections.

Preventing Disease Spread

• Aseptic techniques are procedures used to minimize the risk of contamination.
• Disinfection is the process of eliminating most pathogenic microorganisms.
• Sterilization is the process of eliminating all microorganisms.
• Vaccination is the process of administering a weakened or killed form of a pathogen to trigger an immune response.
• Antibiotics are drugs that kill or inhibit the growth of bacteria.

Test your knowledge on various microorganisms, including bacteria, archaea, fungi, and viruses. This quiz covers key concepts such as Gram-positive classification, nitrogen fixation, and the characteristics of pathogens and prions. Perfect for students of microbiology looking to review important topics.