L39 Microbial growth and behaviour (Winogradsky column)

Choose the incorrect statement about trophic nourishment.

Choose the correct statements about cyanobacteria.

Choose the incorrect statement about green and purple cyanobacteria.

Choose the correct statement about colourless sulfur bacteria(Beggiatoa).

Sulfate reducing bacteria are chemoheterotrophs that essentially reverse the processes that colourless sulfur bacteria carry out.

Organisms which carry out fermentation are [blank_start]chemoheterotrophs[blank_end]. Their energy source, carbon source, and electron donor, are always [blank_start]complex carbons[blank_end] (organic molecules) and sometimes are even the same molecule. An example of [blank_start]a fermenting chemoheterotroph[blank_end] are cellulose degrading bacteria, which break pyruvate down into [blank_start]acetate[blank_end] and simultaneously degrade cellulose into [blank_start]lactate[blank_end]. Other examples include clostridium and [blank_start]rumen[blank_end] bacteria.

Microbial growth in a [blank_start]closed batch[blank_end] culture system is not like nature, in that it is a 'Feast and [blank_start]Famine[blank_end]' situation controlled by the examiner. There are four stages which characterise the growth [blank_start]curve[blank_end] for bacteria in this system. Firstly, there is a [blank_start]lag phase[blank_end]. It is shown as little to no change in the population size. The lag period [blank_start]differs depending[blank_end] on how much the inoculum must evolve and adjust before it is suited to the environment/has the proper [blank_start]biosynthetic reactions[blank_end] taking place. The next phase is the [blank_start]exponential phase[blank_end]. During this phase there are [blank_start]no limited resources[blank_end] or competition and so the bacterial population can [blank_start]double[blank_end] in size every generation via binary fission, displaying exponential population growth. The next phase is the [blank_start]stationary phase[blank_end]. This appears to be a stable population size, but does not indicate static activity. Instead, it reflects the cryptic growth of the organisms. Cryptic growth is the state of [blank_start]dynamic[blank_end] equilibrium where organisms survive by feeding from the lysed, dead bodies of deceased organisms. Finally, there will be a [blank_start]death phase[blank_end] where the population size decreases until it is at a stable end point.

What might cause a persistent bacterial infection?

To be antibiotic resistant a microbe must carry the genes which confer resistance.

Choose the incorrect statement about microbial behaviour.

Which statement best describe the 'sliding' behaviour displayed by myxobacteria.

When a food source is exhausted, myxobacteria form 3D structures of endospores. What are these referred to as?