Microbial Diversity and Microorganism Types: Bacteria, Archaea, Eukaryotes, and Viruses

What is a microbe?

Any microscopic unicellular organism, including bacteria, archaea, and viruses.

What are the three domains of life that microbes exist in?

Eukaryotic, Bacteria, Archaea.

Why is genetic diversity important in understanding biology?

It leads to gene diversity, enzyme diversity, biochemical diversity, and biological function diversity.

What is the Candidate Phyla Radiation (CPR)?

A group representing over 100 unknown bacterial phyla, distant from known bacteria.

What do microbes do in bioconversion?

They convert substances like milk to yogurt and grapes to wine.

What are the main differences between prokaryotic and eukaryotic microbes?

Eukaryotes have membrane-bound organelles and a nucleus; prokaryotes do not.

What are the two main types of prokaryotic microbes?

Bacteria and Archaea.

What are some characteristics of Archaea?

They have unique cell walls, membranes, and gene expression machinery, and many are extremophiles.

What are the four types of extremophiles found in Archaea?

Methanogens, Halophiles, Thermophiles, Psychrophiles.

What is mycology?

The study of fungi.

What are the main characteristics of fungi?

Eukaryotic, do not photosynthesize, have cell walls made of chitin.

What are the three methods of asexual reproduction in fungi?

Spores, budding, and mycelial fragmentation.

What are molds?

Multicellular mycelial masses made up of hyphae.

What is mycorrhizae?

A symbiotic association between plant roots and fungi.

What benefits do fungi provide to plants in mycorrhizae?

Increased mineral nutrients and improved access to water.

What are algae?

Photosynthetic eukaryotic organisms that contain chlorophyll and chloroplasts.

What are phytoplankton?

Photosynthetic microorganisms that form the base of the food chain and produce 70-80% of the planet's atmospheric oxygen.

What are diatoms?

Algae with cell walls made of silica, contributing significantly to atmospheric oxygen.

What distinguishes dinoflagellates?

They possess two flagella and can cause harmful algal blooms known as 'red tide.'

What are Prochlorococcus and Synechococcus?

Cyanobacteria that are not algae but share a common ancestor with plant chloroplasts.

What significant event did cyanobacteria cause?

The great oxygenation event, which changed Earth's atmospheric composition.

What are lichens?

Symbiotic associations between fungi and photosynthetic organisms, such as algae.

What is the role of fungi in ecosystems?

They decompose organic matter and form symbiotic relationships with plants.

What is the significance of microbial genetic diversity?

It contributes to ecological resilience and the ability to adapt to changing environments.

What is the ecological role of algae?

They are primary producers in aquatic ecosystems, contributing to oxygen production and carbon fixation.

What are the main components of fungal cell walls?

Chitin, which provides structural strength.

How do fungi obtain nutrients?

Through absorption after decomposing organic matter.

What is a lichen?

A composite organism that arises from algae (or cyanobacteria) and a fungus in a mutualistic relationship.

What are the mutual benefits of the lichen partnership?

The alga provides increased water availability and protection from drying out, while the fungus provides nutrients derived from photosynthesis.

Where can lichens be found?

On rocks, soil, trees, concrete structures, and rooftops.

What is the outermost layer of a lichen called?

Cortex, which is made of tightly woven fungus filaments (hyphae).

What is the function of the photobiont layer in lichens?

It contains photosynthesizing green algae.

What are rhizines in lichens?

Innermost anchoring hyphae where the fungus attaches to the substrate.

What defines protozoa?

Protozoa are single-celled heterotrophs that are part of the protist group.

What is a heterotroph?

An organism that ingests or absorbs organic carbon to produce energy, rather than fixing carbon from inorganic sources.

What distinguishes protozoa from algae and fungi?

Protozoa are not photosynthetic and do not have a cell wall.

What are mixotrophs?

Protozoa that can perform both phagocytosis and photosynthesis, such as Euglena and Dinoflagellates.

What are pseudopodia?

Temporary projections of the cytoplasm used by amoebas for crawling and feeding.

What is the function of cilia in ciliates?

Cilia are used for cell propulsion and food acquisition.

How do microbes help protect humans?

By occupying space to prevent pathogens and stimulating immune cells.

How do microbes influence human metabolism?

They aid in digestion and fermentation of foods, shaping metabolic rates.

What role do microbes play in detoxification?

They take in toxins and mitigate their dangerous effects.

How do microbes affect infants born via c-section?

They have different microbiomes, making them more likely to develop allergies and asthma.

What is the global carbon cycle's relationship with microbes?

Many bacteria can use CO2 for growth, playing a crucial role in the carbon cycle.

What is the significance of microbes in the ecosystem?

Microbes are essential for life on Earth, influencing various ecological processes.

What is the shape characteristic of amoebas?

Amoebas have no distinct shape due to the lack of a cell wall or exoskeletal structure.

What is the role of Paramecium in protozoan studies?

Paramecium is a well-studied protozoan known for its oral groove for food ingestion.

What role do soil bacteria play in the nitrogen cycle?

They convert nitrogen into a form that plants can use for growth.

What significant event did cyanobacteria contribute to around 2.5 billion years ago?

The great oxidation event.

What are some examples of pollution that microbes help clean up?

Gasoline leaks, oil spills, nuclear waste, sewage, and other pollutants.

What is the resolution limit of the human eye?

Approximately 0.1 mm.

What is the difference between resolution and detection?

Resolution is the smallest distance by which two objects can be separated and still distinguished, while detection is the ability to determine the presence of an object.

What is the size range of eukaryotic microbes?

10-100 micrometers.

What are the common shapes of prokaryotic cells?

Cocci (spheres), bacilli (rods), spirilli (rigid spirals), spirochetes (flexible spirals), and appendaged (protrusions).

What is the resolution limit of light microscopy?

200 nm.

What is the purpose of immersion oil in microscopy?

It minimizes the loss of light rays by refraction, allowing for higher magnification with minimal distortion.

What is a compound microscope?

A system of multiple lenses designed to correct or compensate for aberration.

What is the advantage of using a wet mount preparation for microscopy?

It allows for the observation of cells in their natural state and is quick to prepare.

What is the most famous differential stain used in microbiology?

The Gram stain.

What distinguishes Gram-positive bacteria from Gram-negative bacteria?

Gram-positive bacteria retain the crystal violet stain due to their thicker cell wall, while Gram-negative bacteria do not.

What is the function of dark field microscopy?

It uses scattered light for detection, visualizing specimens as halos of bright light against darkness.

How does phase-contrast microscopy enhance visibility of cellular structures?

It exploits differences in refractive index between the cytoplasm and surrounding medium.

What is differential interference contrast microscopy (DIC) used for?

To enhance contrast and provide a false 3D effect by superimposing an image of the specimen onto a second beam of light.

What is the principle behind fluorescence microscopy?

The specimen absorbs light of a defined wavelength and emits light of lower energy, thus fluorescing.

What is the purpose of color filters in fluorescence microscopy?

They select the excitation wavelength for the light passing through the specimen.

What is the primary function of the cell membrane?

It defines the existence of a cell and regulates transport in and out of the cell.

What are the two major types of electron microscopy?

Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM).

What does TEM reveal?

Internal structures of cells by allowing electrons to pass through the specimen.

What does SEM reveal?

External features of specimens in 3D by scanning the specimen surface with electrons.

What is a fluorophore?

A fluorescent chemical compound used to label cell parts.

How can fluorescence be introduced into cells?

It can be genetically encoded or added as a chemical dye.

What is the role of membrane proteins?

They provide structural support, detect environmental signals, and facilitate transport.

What is the difference between passive and active transport?

Passive transport moves molecules along their concentration gradient, while active transport moves them against it, requiring energy.

What is the biochemical composition of bacteria?

Bacteria consist of water, essential ions, small organic molecules, macromolecules (DNA, RNA, proteins), and peptidoglycan.

What are the components of a bacterial cell membrane?

Half of the membrane is protein, with varying phospholipid structures.

What are the main types of microscopy used to observe live bacteria?

Atomic Force Microscopy (AFM) and Cryo-Electron Microscopy (cryo-EM).

What is the significance of cryo-electron microscopy?

It allows imaging without staining and requires specimens to be flash-frozen.

What are the characteristics of archaea compared to bacteria?

Archaea have unique membranes, enveloped structures, and gene expression machineries.

What enhances the fluidity of cell membranes?

Unsaturated fatty acid chains and kinks in the chains.

What is the role of peptidoglycan in bacterial cells?

It provides structural support and shape to the bacterial cell wall.

What is the function of transport proteins in the cell membrane?

They facilitate the movement of polar and charged molecules across the membrane.

What is the purpose of tomography in microscopy?

It combines tilt series images to create a 3D image and can use color reconstruction.

What are the main components of a bacterial cell?

Water, proteins, RNA, lipids, DNA, metabolites, and inorganic ions.

What is the impact of membrane lipid diversity in archaea?

It maintains membrane stability under extreme environmental conditions.

What is the significance of using heavy metals in electron microscopy?

Samples must be coated with heavy metals to absorb electrons for imaging.

What is the primary difference between prokaryotic and eukaryotic cells?

Prokaryotic cells lack a membrane-bound nucleus, while eukaryotic cells have one.

What is the role of ion transport in cell membranes?

It is crucial for maintaining cellular homeostasis and energy storage.

What is the primary function of the cell wall in prokaryotes?

The cell wall confers shape and rigidity and helps the cell withstand turgor pressure.

What is the composition of most bacterial cell walls?

Most bacterial cell walls are made up of peptidoglycan.

What are the two types of bacteria based on cell wall structure?

Gram-positive bacteria (thick cell wall) and Gram-negative bacteria (thin cell wall).

What is the role of teichoic acids in Gram-positive bacteria?

Teichoic acids thread through multiple layers of peptidoglycan and help the cell retain the Gram stain.

What is the function of the capsule in bacteria?

The capsule protects cells from phagocytosis and helps prevent drying out.

What is unique about mycoplasma in terms of cell structure?

Mycoplasma have a cell membrane with no outer layers and no cell wall.

What defines the cell envelope of Gram-negative bacteria?

A thin peptidoglycan layer and an outer membrane that provides defensive abilities.

What are lipopolysaccharides and where are they found?

Lipopolysaccharides are found in the outer membrane of Gram-negative bacteria and contribute to their toxigenic properties.

What is the nucleoid in prokaryotic cells?

The nucleoid is a region that contains a condensed circular chromosome with proteins and RNA.

How does transcription and translation occur in prokaryotes?

Transcription and translation are coupled; mRNA is immediately bound by ribosomes for translation.

What is the role of the replisome in bacterial DNA replication?

The replisome is a protein complex that synthesizes DNA at the replication forks.

What triggers the growth of the septum during cell division?

Replication of the termination site (Ter) triggers the growth of the dividing partition, or septum.

What is FtsZ and its role in cell division?

FtsZ is a Tubulin-like GTPase that forms a 'Z-ring' which initiates cell division.