Lecture 38 Flashcards
Why are bacteria so dominant in the worlds biomass?
They have a fast growth time, allowing for fast evolution/adaptation and have been around for billions of years (allowing colonization of every environment on the planet).
Give examples of what bacteria can grow on.
Essentially anything: plant tissue, animal tissue, excretory products, cells of dead bacteria, heavy metals, antibiotics etc. They will typically break down polymers like starch, cellulose, polysaccharides, proteins, organic matter into simple monomers like glucose, but not always.
How do bacteria reproduce?
Asexually via binary fission, this results in two genetically identical daughter cells.
What do bacteria need to grow?
A bacterial cells needs to be able to generate energy, precursor metabolites (building blocks) and a reducing power.
As such they need an energy source (typically to produce ATP), a carbon source and a reducing source like NADH/NADPH. (NADH is the reduced form, NAD is the oxidised form).
What are the terms for energy consumption and generation? What do they typically produce?
Catabolism is energy generation and produces byproducts from substrates and ATP. Anabolism is energy consumption and uses ATP to produce macromolecules and other cellular constituents from monomers (substrates).
What are the different trophic groups?
Photo (using light as the energy source), chemo (using chemical compounds as the energy source), auto (using carbon dioxide as the carbon source), hetero (using organic compounds as the carbon source), the carbon source and energy source are often combined to give the full group e.g chemoautotrophs use chemical compounds for energy and carbon dioxide as the carbon source.
What is an organic compound? What about inorganic? What are the common examples?
Organic contains C-H bonds (e.g glucose), inorganic does not e.g H2S.
What are the microbial growth stages in a closed batch culture system? Describe them.
The lag phase (length which depends on the history of the inoculum, this is because time is needed to get the biosynthetic reactions running). Exponential (cells actively dividing and nothing limits growth, population doubles in a constant time interval). Stationary (cells stop growing and slowed growth is observed, as much replacement as there is death, typically caused by something limiting growth like food, space or a toxic end product). Death phase (cells die off, some persisters will remain towards the end).
What are persister bacteria? Why can’t penicillin kill them?
Bacteria which stop dividing, these are the last ones surviving and penicillin can’t kill them because it acts when they are dividing or about to. These cells are genetically identical to the others but are protected from the penicillin due to their stopping growth and can lead to persistent infections.
Give some examples of bacterial organisation.
Myxobacteria: social gram negative bacteria which can behave like multicellular organisms. Can perform social gliding motility or development of fruiting bodys (environmentally resistant spores). They can move either forwards or backwards by changing polarisation and using their A engine (slime secretion) or S-engine (pili which pull the cell).
When are fruiting bodies formed and why?
If food runs out myxobacteria will stop swarming and congregate inwards, coordinated movements will take place mediated by cell signalling and will aggregate around the fruiting body. When nutrients become available the myxospores will germinate and the growth cycle will begin again.
