MBIO162 Microbial Diversity

What are microbes?

Microscopic organisms too small to be seen with the naked eye, including bacteria, archaea, unicellular protists, fungi, and viruses.

How long have microbes been on Earth?

Microbes have been on Earth for approximately 3.8 billion years.

What is the age of the Earth?

The Earth is approximately 4.5 billion years old.

What distinguishes microorganisms according to some scientists?

Small size, unicellular organization, and feeding by osmotrophy.

What is an exception to the characteristics of microorganisms?

Some microscopic unicellular protists feed by phagotrophy.

What is the common ancestor for all living organisms?

All living organisms share a common ancestor based on the pathway for the flow of information.

What does LUCA stand for?

LUCA stands for Last Universal Common Ancestor.

What hypothesis explains the origin of life related to hydrothermal vents?

Life arose from gases harnessing energy from geochemical gradients at deep-sea hydrothermal vents.

What are stromatolites?

Microbial formations found in rocks younger than 3.5 billion years.

What role does RNA play in the evolution of life?

RNA may have been the first self-replicating molecules, having catalytic properties.

How did DNA take over the role of RNA?

DNA became the more stable repository of coding information as proteins emerged.

What comprises the domain Bacteria?

Bacteria are classified based on phenotypic, genotypic, and phylogenetic properties.

What is the definition of a bacterial species?

A group of bacteria with more than 70% DNA-DNA hybridization and 97% similarity in 16S rRNA gene sequences.

What are oligotrophs?

Planktonic bacteria that are genetically programmed to adapt to low nutrient conditions.

What is the role of SAR11 clade?

Dominates ocean surface bacterioplankton and accounts for a significant portion of pelagic microbes.

What are cyanobacteria known for?

Cyanobacteria are photosynthetic and can fix nitrogen, contributing significantly to global CO2 fixation.

What are methanogens?

Obligate anaerobes that produce methane, found in Euryarchaeota.

What is the significance of viral lysis in the ocean?

Viral lysis stimulates nutrient cycling and increased bacterial production in marine environments.

What do the Haptophytes consist of?

Major marine phytoplankton group, forming significant impacts on oceanic processes.

Differentiate between phagotrophy and osmotrophy.

Phagotrophy involves engulfing particles, while osmotrophy involves absorption of soluble nutrients.

How do ciliates capture food?

Ciliates use cilia to create currents that channel food into the cell.

What defines the kingdom Fungi?

Fungi are a diverse group of organisms, often microscopic, with various ecological roles.

What are chytrids?

Unicellular fungi that can be parasites or saprotrophs, with a life cycle that includes swimming zoospores.

What is the ecological role of zoospores in chytrids?

Zoospores swim to new substrates to initiate the growth of new sporangium.

What is the Dikarya?

A group of fungi characterized by an increase in complexity and a variety of ecological roles.

Define the concept of the phylogenetic tree.

A diagram illustrating the inferred evolutionary relationships among biological species.

Which scientist pioneered the classification of life into three domains?

Carl Woese in the 1970s.

What evidence supports the endosymbiotic theory?

Organelles like mitochondria and chloroplasts possess their own genomes and are genetically similar to bacteria.

Identify the major groups of Alveolates.

Ciliates, dinoflagellates, and apicomplexans.

What special characteristics do dinoflagellates possess?

They have a unique mode of feeding using a pseudopodial 'feeding veil' and secrete digestive enzymes.

What are foramminiferans?

Shell-like organisms within the Rhizarians group.

Explain the function of cilia in ciliates.

Cilia allow for movement and the creation of water currents for feeding.

What is the significance of the rosebacter clade?

A dominant component in coastal and ocean bacterioplankton, playing a role in biogeochemical cycles.

What is unique about the Vibrio species?

Curved rod bacteria found in marine environments, with many being bioluminescent.

Describe the survivor strategy of obligate hydrocarbonoclastic bacteria (OHCB).

They thrive on oil pollution and help break down hydrocarbons in affected environments.

What is the role of Chemoautotrophic bacteria in hydrothermal vents?

They utilize chemical energy from reduced sulfur compounds to thrive in extreme environments.

What organism is known as the most prominent nitrogen fixer in the ocean?

Trichodesmium is a major nitrogen fixer found in tropical and subtropical oceans.

How do marine lichens contribute to nitrogen fixation?

Some form symbiotic relationships with cyanobacteria, aiding in nitrogen fixation.

What do the marine stramenopiles include?

They include diatoms, brown algae, and important parasites.

What is the structure that encloses diatoms?

Diatoms are enclosed within a hard silica 'shell' called a frustule.

What is an example of a well-known algae?

Kelp is an example of 'well-known' macroalgae.

What type of environment do Centrohelids primarily inhabit?

Centrohelids are mainly found in freshwater environments.

What distinguishes eukaryotic cells?

Eukaryotic cells are characterized by having a nucleus.

What is the ecological importance of fungal lichens?

Lichens indicate environmental health and contribute to nutrient cycles.

How do choanoflagellates feed?

They use a flagellum to draw water through a collar of tentacle-like filaments to trap bacteria.

What is the impact of methanogenesis on climate?

Methane is a potent greenhouse gas, contributing to climate change when released.

What role do hydrothermal vent species play in nutrient cycling?

They support unique ecosystems and contribute to the recycling of nutrients in extreme environments.

What is meant by microbial diversity?

The variety of different microbial species and their functional roles in ecosystems.

What are the primary characteristics of the Euryarchaeota?

Euryarchaeota are known for their metabolic diversity, including methanogens.

What is the concept of phylogenetics based on?

Phylogenetics relies on genetic similarities and differences to establish evolutionary relationships.

How do filamentous bacteria like Thiomargarita store nutrients?

Thiomargarita stores nitrate in large vacuoles and sulfur in granules.

What roles do both phototrophs and chemolithotrophs play in microbial ecosystems?

Phototrophs harvest light to produce energy, while chemolithotrophs oxidize inorganic compounds for energy.

What is the significance of the phosphorus cycle in aquatic systems?

The phosphorus cycle is crucial for nutrient cycling, impacting ecosystems and productivity.

How do oceanic bacteria contribute to the cycling of organic material?

Bacteria decompose organic matter, recycling nutrients back into the ecosystem.

How are microbial cells measured in relation to human cells?

Humans are composed of ten times more microbial cells than human cells.

What environmental conditions hindered the early evolution of life on Earth?

Extreme temperature fluctuations, meteor impacts, and intense UV radiation made conditions hostile.

What is the role of viruses in microbial populations?

Viruses can regulate bacterial populations and influence nutrient cycling in ecosystems.

What type of lifestyle do particle-associated copiotrophs exhibit?

They have a ‘feast or famine’ lifestyle, rapidly growing in nutrient-rich conditions.

How does the structure of a phylogenetic tree relate to evolutionary history?

The branching patterns in a phylogenetic tree represent the evolutionary divergence of species.

What is the main characteristic of archaeplastids?

They contain primary plastids derived from endosymbiosis with cyanobacteria.

How do varied ecological roles of fungi manifest in ecosystems?

Fungi can be parasites, saprotrophs, symbionts, and play critical roles in decomposition.

Identify a function of rhizarians.

Rhizarians are often amoeboid protists that can play roles in nutrient cycling.

How do phagotrophic organisms differ from osmotrophic ones?

Phagotrophic organisms engulf food particles, while osmotrophic organisms absorb nutrients.

What adaptations do oligotrophs exhibit?

Oligotrophs have small sizes and slow growth rates adapted for low nutrient environments.

What do the major genera associated with Vibrio include?

Major genera include Vibrio, Photobacterium, and Aliivibrio.

What are the ecological roles of saprotrophic fungi?

They decompose organic matter, recycling nutrients back into the ecosystem.

How widespread is the use of rRNA in phylogenetic studies?

16S rRNA gene sequencing is commonly used for determining the evolutionary relationships among bacteria.

Identify one knowledge gap in the study of marine stramenopiles.

Some abundant taxa are not well characterized or successfully cultured.

What are two main trophic modes of chytrids?

Chytrids can be either parasites or saprotrophs.

Describe the ecological role of myxobacteria.

Myxobacteria are known for their complex social behavior in nutrient-rich environments.

What distinguishes the marine stramenopiles from diatoms?

Diatoms are a specific subgroup within marine stramenopiles known for their silica frustules.

How can the life cycle of Chytrids impact host species?

Chytrids often kill their hosts, such as in the case of infections in frogs.

What information does phylogenetic classification of Bacteria rely on?

Phylogenetic classification relies on genetic and molecular characteristics.

What defines the phylum Proteobacteria?

Proteobacteria is a diverse group of bacteria encompassing various metabolic types, including many pathogens.

What is characteristic of the phylum Firmicutes?

Firmicutes are characterized by their thick cell walls and can be found in various environments, often involved in fermentation.

What distinguishes the phylum Actinobacteria?

Actinobacteria are known for their filamentous structure and play crucial roles in soil health and antibiotic production.

What are the main features of the phylum Bacteroidetes?

Bacteroidetes primarily function in the degradation of complex carbohydrates and are abundant in the human gut.

How do members of the phylum Spirochaetes differ from other bacteria?

Spirochaetes are distinguished by their unique spiral shape and motility through axial filaments.

What is unique about members of the phylum Chlamydiae?

Chlamydiae are obligate intracellular bacteria that reproduce within host cells and cause various diseases.

Describe the phylum Cyanobacteria.

Cyanobacteria are photosynthetic bacteria known for their role in producing oxygen and fixing nitrogen.

What is a key feature of the phylum Verrucomicrobia?

Verrucomicrobia are known for their unique morphology and ability to degrade complex polysaccharides.

What is the ecological role of the phylum Planctomycetes?

Planctomycetes have unique cell structures and are involved in nutrient cycling in aquatic environments.

What characterizes the phylum Acidobacteria?

Acidobacteria are typically found in acidic soils and are important for ecological health due to their metabolic diversity.