2 Microbes - Terms

Microbe

A single-celled, microscopic organism, including bacteria, archaea, viruses, and some eurkaryotes.

Spontaneous generation

The theory that living cells emerge spontaneously from non-living matter.

Symbiosis

Two or more organisms of different species living together in close proximity. Can include beneficial, neutral or harmful (e.g. parasitism) relationships.

Cell

An individual biological unit capable or metabolism and reproduction, bounded by a plasma membrane and containing a genome.

Genome

The entire genetic content of a cell, including the chromosome and any extra-chromosomal elements like plasmids. Genomes can be made up of DNA or RNA.

Transcription

The process of synthesizing a single-stranded mRNA molecule from a coding sequence of DNA (a gene) in the genome.

Ribosome

A complex of RNA and protein that translates mRNA into protein

Translation

The process of synthesizing a protein as a specific sequence of amino acids specified by codons in mRNA

mRNA (messenger RNA)

A long RNA molecule transcribed from DNA, consisting of codons.

Codon

A specific sequence of 3 consecutive nucleotides that encode a specific amino acid or the ‘start’ or ‘end’ of translation

Protein

A string of specific amino acids that fold into a specific 3-dimensional structure that determines its biological function (e.g enzyme, structural, etc).

Horizontal gene transfer

The transfer of genetic material between organisms rather than from parent to offspring.

Natural selection

The process by which heritable traits that improve survival or reproduction become more common in a population over generations.

Autotroph

An organism that produces their own food

Heterotroph

An organism that uses organic carbon

• unable to produce organic substances from inorganic substances

Phototroph

An organisms that gets its energy from light

Oxidation

Loss of electrons by a molecule.

Reduction

Gain of electrons by a molecule

Redox

The coupling of oxidation and reduction ‘half-reactions’ into a single chemical reaction, releasing energy

Respiration

The process of oxidizing organic compounds using a terminal electron acceptor such as oxygen (in the case of aerobic respiration), sulphate or nitrate (in the case of anaerobic respiration).

LUCA

most recent common ancestor of all life living on Earth today

evidence: all life on earth is:

• carbon-based

• has similar enzymes w/ similar gene recipes

• passes heredity information through DNA/RNA

• universal genetic code

Ribozyme

An RNA molecule that catalyses a chemical reaction.

Stromatolite

macroscopic structures formed by formed through the activity of microbial mats, either fossilized or living.

Microbial mat

layered community of microorganisms growing together on a surface

held together by “slime”

Biosignature

evidence that may indicate the presence of past or present life.

Molecular biomarker

an organic molecule preserved in rocks or sediments that can provide evidence about past life.

Anoxygenic photosynthesis

photosynthesis that does not produce O₂ and uses electron donors other than water.

Oxygenic photosynthesis

photosynthesis that uses H₂O as an electron donor and produces O₂.

Cyanobacteria

Bacteria capable of oxygenic photosynthesis.

Great Oxidation Event

the interval when O₂ first accumulated substantially in Earth's atmosphere.

Prokaryote

An organism whose cells lack a membrane-bound nucleus.

Eukaryote

organism whose cells contain DNA within a membrane-bound nucleus and other membrane-bound organelles. A domain of life of Earth.

Endosymbiosis

A relationship in which one organism lives inside another; central to the origin of mitochondria and chloroplasts.

Eukaryogenesis

The evolutionary process that gave rise to the eukaryotic cell and lineage.

Archaea

Single-celled microorganisms that are evolutionarily distinct from bacteria.

Asgard archaea

A group of archaea that are the closest known archaeal relatives of eukaryotes.

Metagenomics

Sequencing DNA directly from an environmental sample without first culturing the organisms.

Horizontal gene transfer (HGT)

Movement of genetic material between organisms rather than from parent to offspring.

Vertical inheritance

Transmission of genetic material from parent to offspring.

Species tree

A phylogenetic tree showing the evolutionary relationships among organisms.

Gene tree

A phylogenetic tree showing the evolutionary history of a particular gene.

Virus

Genetic material enclosed in a protein coat that requires a host cell to replicate.

Phage

A virus that infects bacteria or archaea

gene transfer (horizontal & vert)

allows microbes to quickly gain new traits and adapt