microbial stress

Question 1

when does stress affect microbes

Answer 1

when the level exceeds the tolerance threshold

Question 2

what is adaptive response

Answer 2

exposure to non-lethal levels which give extra resistant for subsequent, larger infections by upregulating stress resistance genes

Question 3

what is cross tolerance and what are the two ways in which it can work

Answer 3

exposure to one type of stress shows elevated resistance to another type of stress. this can either be because the upregulated genes confer resistance to more than one stress type of because the response it to upregulate a general stress response pathway

Question 4

how is stress sensed

Answer 4

usually via membrane bound receptors, though bacteria often use two component systems

Question 5

what is the stress response to cold temperature

Answer 5

synthesis of cryoprotectants which stabilise the membrane and the upregulation of desaturase enzymes as desaturated fatty acids maintain the membrane’s fluidity

Question 6

what is the stress response to high temperature

Answer 6

synthesis of heat shock proteins and trehalose which stabilises macromolecules

Question 7

how does osmotic pressure cause stress

Answer 7

it either causes water to be taken in (hypo osmotic) or leaked (hyper osmotic) which damages the cells and created an environment which isn’t optimal for protein function

Question 8

what is the stress response to osmotic pressure

Answer 8

cells synthesise or take up compatible solutes to restore the osmotic balance, synthesise trehalose, and in cases of hypo osmotic pressure they may expand the cell wall/ membrane to increase cell capacity

Question 9

how does oxidative pressure cause stress

Answer 9

when reactive oxygen species ROS are produces at a rate that exceeds antioxidative capacity. they cause damage to DNA, lipids and proteins

Question 10

what is the stress response to oxidative stress

Answer 10

upregulate genes for ROS scavengers and enzymes which repair the oxidative damage