carbohydrate sources & usage

class 4

preferred carbon source

glucose; bacteria use it first because it is the most energy-efficient

catabolite repression

a regulatory system where the presence of glucose represses genes for alternative carbon source utilization

alternate carbohydrates

non-glucose carbon sources like lactose, chitin, and cellulose

induction

activation of gene expression in response to the presence of a specific substrate

diauxic growth

two-phase growth pattern where glucose is used first, followed by an alternative carbon source

operon

a group of genes transcribed together as a single mRNA and regulated by one control system

lac operon

an operon that controls lactose uptake and metabolism in E. coli

lacZ

gene encoding B-galactosidase, which breaks lactose into glucose and galactose

lacY

gene encoding lactose permease, which transports lactose into the cell

lacA

gene encoding thiogalactoside transacetylase (minor role in lactose metabolism)

lactose permease (LacY)

a symporter that transports lactose into the cell along with a proton

B-Galactosidase

enzyme that cleaves lactose into glucose and galactose

allolactose

a lactose derivative that acts as the truse inducer of the lac operon

lac repressor

a protein that binds the operator to block transcription when lactose is absent

IPTG

a non-metabolizable lactose analog used to experimentally induce the lac operon

polysaccharides

long chains of sugars, such as cellulose and chitin, used as carbon sources by some bacteria

cellulose

structural polysaccharide found in plants; difficult to degrade

chitin

the second most abundant biopolymer; found in insect exoskeletons and crustacean shells

chitinase

enzyme that degrades chitin into usable sugar units

N-acetylglucosamine (GlcNAc)

the monomer released from chitin degradation and used as a carbon source

chitoporin

outer membrane protein that allows chitin breakdown products into the cell

phosphotransferase system (PTS)

a transport system that imports sugars while phosphorylating them

vibrio cholerae

a bacterium that causes cholera and survives in aquatic environments using chitin

biofilm

a structured bacterial community attached to a surface and embedded in a matrix

chitin-induced gene expression

activation of genes for chitin degradation, transport, and metabolism when chitin is present in the

bioremediation

the use of microorganisms to remove or degrade environmental pollutants

organophosphates

pollutant compounds that can be degraded by certain bacteria

alcanivorax borkumensis

a bacterium that degrades hydrocarbons, especially in oil spills

autotroph

an organism that produces organic compounds using CO2 as a carbon source

energy pathways as drug targets

essential for survival and harder for bacteria to bypass

metabolic flexibility

allows bacteria to survive in changing environments and nutrient availability

importance of lac operon

demonstrates gene regulation, induction, and efficient resource use

why glucose is used first

it provides the most efficient energy yield and represses alternative pathways