Question

• • How do nutrients get into the microbial cell?
• please write without hand
• thank you

Answer 1

There are various Methods of Nutrient uptake in Microbial cells .

1. Passive Diffusion - It is the process of movement of small molecules of high concentration to low concentration . Example - Movement of CO_{​​​​​2} and H_{​​​​​​2O .}

2. Facilitated Diffusion - It is also a kind of Diffusion which involves carrier proteins and rate of Diffusion increases with the increase of concentration gradient . Major Intrinsic proteins (MIP) helps in the Diffusion of small polar molecules . Example - Glycerol get transported by facilitated Diffusion. Channel protein - permease which helps in the uptake of lactose in bacteria.

3. Osmosis - It is the process of flow of solvent molecules through a selectively permeable membrane from higher concentration to lower concentration untill the equillibrium is reached . On the basis of osmolarity there are three types of solution i.e Hypertonic , Isotonic and Hypotonic.

4.​​​​​4.Active Transport - It is transport molecules against a concentration gradient using metabolic energy . Example - ABC ( ATP binding cassete transporters) Transporters .

ABC Transporters - A functional ABC transporter has two transmambrane domains (TMDs) and two cytosolic nucleotide binding domain (NBDs) . They utilize energy derived from ATP hydrolysis to transport molecules . These transporters have special substrate binding proteins attached to membrane lipids and located in periplasmic space of gram +ve and -ve bacteria respectively. Example -Transport of sugars ( ribose , arabinose , galactose and maltose ) and amino acids takes place by this mechanism in E.coli . Another example is P- glycoprotein - Multidrug resistance protein 1.

Group Translocation - It is a process in which molecule is transported in a cell after modifying it chemically . Example - Phosphoenolpyruvate (PEP) ; sugar phosphotransferase system (PTS) . It transport sugar by phosphorylating them using PEP as phosphate donor.

Iron Uptake - To uptake iron many bacteria and fungi secrete Siderophores : These are small organic molecules which when completed with ferric ion transport it into the cell. 3 molecules of Siderophores bind with 1 Fe atom via 6 coordinate bonds .

Example - Hydroxymates - ferrichrome ( Released by fungi ).