L4 Flashcards
What is a microbe?
An organism too small to be seen by the eye. They may exist in single-celled form or in a collection of cells (microbiome). Microbes come in many different shapes and sometimes form chains, filaments or aggregates
Are all microbes microscopic?
Some can be seen with the naked eye.
What are the main groups of microbes?
Fungi, protists, bacteria, archaea, viruses.
How can microbes be classified?
Into theee domains : eukarya, bacteria, archaea. Microbes are more phylogenetically diverse than plants and animals.
What do eukaryotic microbes include?
Fungi, algae, protists. Yeasts are microbes. Some algae are unicellular but others are pluricellular.
How long have microbes been on earth?
4 billion years. LUCA gave rise to prokaryotic cells. Bacteria and archaea branched soon after life began. Microbial life was anaerobic until the emergence of Cyanobacteria. Cyanobacteria photosynthetic bacteria - produce O2 as a by product. Oxygenation of atmosphere caused mass extinction of anaerobic life, atmospheric oxygen gave rise to aerobic bacteria and eukaryotic microbes. Microbial life dominated the planet for the first 3 billion years, until the first multicellular eukaryotes emerged.
What are mutations and how do they happen?
Changes in the nucleotide sequence of an organisms genome. Occur due to errors in replication, UV radiation, and other factors, organisms adapt to new conditions using mutations, mutation rates are generally constant over time.
What are the 3 main mutations?
Insertion, deletion, substitution
What are 3 more mutations?
Silent - does not affect amino acid sequence, missense - amino acid changed ; polypeptide altered, nonsense mutation - codon becomes stop codon ; polypeptide is incomplete
What are frameshift mutations?
Insertion or deletion they cause more dramatic changes in DNA. They result in shift in the reading frame or loss of complete gene function. Point mutations are typically reversible. Alteration in DNA that reverses the effects of a prior mutation.
What is recombination? What are the processes named in prokaryotes and eukaryotes?
Physical exchange between genetic elements. Prokaryotes it’s called transformation, transduction, conjugation. Eukaryotes it’s called meiosis.
What was the evolution of cell power?
All organisms living on earth are descended from LUCA. LUCA is not the first living organisms on earth it is the one that didn’t hit an evolutionary dead end. Bacteria and archaea branched first with eukarya branching from archaea. At some point one ancestral eukaryotic cell acquired a bacteria endosymbiont, which evolved to be the mitochondria
How does an endosymbiont got to form organelles?
Endosymbiont lysis or DNA escape during endosymbiont division -> genetic transfer to the nucleus. Both the endosymbiont and the nucleus made the same proteins -> genetic redundancy. Evolution of protein translocation machinery -> proteins can be transported to the protoorganelle. Gene loss in the organelle.
How does it go from bacteria to mitochondria?
Gene loss in mitochondria resulted in - specialised for energy production, each mitochondrion produces as much ATP as a bacteria, but at the fraction of the normal bacteria cost. Eukaryotic cells having 100,000 times more energy per gene than available in bacteria. Eukaryotic cells supporting larger genomes, make more proteins from each gene and retain large families of duplicated genes to craft new functions. Organelle genomes are usually circular DNA molecules. Organelles genomes encode some but not all the proteins used in the organelle. In sexual reproduction mitochondrial genome is inherited from the mother as mitochondria in the sperm is usually destroyed by the egg cell after fertilisation.
Why are microbes so abundant?
Small size, simple design, reproduce fast and adapt quickly, been around for long time.
How do microbes impact the planet?
They can live in harsh environments such as soil or thrive under harsh conditions. Extremes of the temperature ranges, high hydrostatic pressures, high salt concentrations, extreme pHs.
How are microbes earth greatest allies?
Sustain life by carrying out transformation of matter essential to life. Bacteria originally oxygenated earths bacteria. Cyanobacteria and algae replenish the atmosphere with oxygen. Participate in the decomposition of organic matter without microbes CO2 accumulates in dead matter. Helps plants fix atmospheric nitrogen making it available for other organisms.
How do microbes help sequester atmospheric CO2?
Atmospheric CO2 enters the ocean where it can 1) be converted into organic carbon via photosynthesis. 2) react with seawater to form carbonic acid. Carbonic acid dissociates to form carbonate and bicarbonate, this leads to release and therefore increase in H+ lower the pH of seawater. The additional carbonate required to create bicarbonate decreases the available carbonate. Without microbes CO2 enter the ocean via route 2. Oceans are slightly alkaline but ocean acidification can result when the pH moves toward the acid end of the scale, due to an increase in H+. Reduced carbonate means marine organisms have a harder time making new shell and maintaining the ones they’ve already got.
How do microbes carry out geological processes - coccolithopores?
Produce oxygen, sequester CO2 and are food source. Coccolithopores use calcium carbonate to form tiny plates, or scales. Calcite is the main constituent of limestone.
How do microbes carry out geological processes - formation of cavern structures
Cavern structures can be formed because of microbial activity, microbes oxidise hydrogen sulphide to sulphuric acid. Sulphuric acid dissolves calcium carbonate which is washed away by water.
How can microbes affect cloud formation?
Marine algae and bacteria produce DMS and DMSP. DMS turns into sulfate in the atmosphere. Sulphate acts as a nucleating agent for water vapour to become water droplets. Clouds are formed.
How do microbes have symbiotic relationships with mammals?
Mammals do not produce the enzymes that breakdown cellulose in plant material. Cattle harbor cellulose digesting microbes in their rumen which break it down into volatile fatty acids, the animal uses as a major source of energy. Animals provide microbes with a suitable habitat for growth.
How do microbes have symbiotic relationships with termites?
Termites have bacteria in their guts that break down cellulose but also the termites produce cellulases.
What influences do microbes have in daily life?
Carry out industrial activities - bread, wine, beer etc
Produce medically supported proteins - vaccines
Provide public health measures - sewage treatment
Biomediation of polluted sites - oil spill cleanup with oil-degrading microbes
What is a closed ecosystem?
Where plants and animals could live in a self-sustained manner.
What did the biosphere 2 project investigate?
The viability of a close ecological system to support and maintain life in outer space. After 16 months biosphere 2 dropped by half and flora and fauna began to die. The atmospheric oxygen was disappearing at rate much faster than predicted, the topsoil contained two to five times more peat and compost than typical soil. Bacteria are most numerous in compost, metabolising organic matter and in the process consuming oxygen and producing CO2. As a closed ecosystem the plants should have been able to use the excess CO2 to produce O2 however there were two main problems. 1) photosynthetic rates were low as the glass cover was blocking more than half the available sunlight 2) not enough CO2
Biosphere project 2 - why was there so little CO2 given the high soil bacterial activity?
CO2 was being sequestered by calcium hydroxide, in the concrete used to make the domes, to produce calcium carbonate instead of being consumed by the plants to make more oxygen.
What are other examples where microbes used up all the oxygen?
Fertiliser run-off ends up being transported by rivers eventually reaching the ocean. Algae and Cyanobacteria thrive in the nutrient rich water causing oxygen depletion and loss of macrofaunal.
