bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinians, Augustinian ...

, the mal regulon is a

regulon In molecular genetics, a regulon is a group of genes that are gene regulation, regulated as a unit, generally controlled by the same regulatory gene that gene expression, expresses a protein acting as a repressor or activator (genetics), activator ...

- or group of

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

s under common

regulation Regulation is the management of complex systems according to a set of rules and trends. In systems theory, these types of rules exist in various fields of biology and society, but the term has slightly different meanings according to context. Fo ...

- associated with the

catabolism Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipid ...

maltose } Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the tw ...

and

maltodextrin Maltodextrin is a name shared by two different families of chemicals. Both families are glucose polymers (also called ''dextrose polymers'' or ''Dextrin, dextrins''), but have little chemical or nutritional similarity. The digestible maltodextr ...

s. The system is especially well characterized in the

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

Escherichia coli ''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Escherichia'' that is commonly fo ...

'', where it is classically described as a group of ten genes in multiple

operon In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splic ...

s whose expression is regulated by a single regulatory protein,

malT Malt is any cereal grain that has been made to germinate by soaking in water and then stopped from germinating further by drying with hot air, a process known as "malting". Malted grain is used to make beer, whisky, malted milk, malt vinegar, ...

. MalT binds to maltose or maltodextrin and undergoes a

conformational change In biochemistry, a conformational change is a change in the shape of a macromolecule, often induced by environmental factors. A macromolecule is usually flexible and dynamic. Its shape can change in response to changes in its environment or othe ...

that allows it to bind

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

at sequences near the promoters of genes required for uptake and catabolism of these sugars. The maltose regulation system in ''E. coli'' is a classic example of positive regulation. malT is regulated by catabolite repression via the

catabolite activator protein In cell biology, catabolite activator protein (CAP), which is also known as cAMP receptor protein (CRP), is a trans-acting transcriptional activator in bacteria that effectively catalyzes the initiation of DNA transcription by interacting with ...

. Genes under the control of malT include

ATP-binding cassette transporter The ABC transporters, ATP synthase (ATP)-binding cassette transporters are a transport system superfamily that is one of the largest and possibly one of the oldest gene family, gene families. It is represented in all extant taxon, extant Phyl ...

components, maltoporin, maltose binding protein, and several

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

s. Other

Gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

bacteria such as ''

Klebsiella pneumoniae ''Klebsiella pneumoniae'' is a Gram-negative, non-motile, encapsulated, lactose- fermenting, facultative anaerobic, rod-shaped bacterium. It appears as a mucoid lactose fermenter on MacConkey agar. Although found in the normal flora of the mo ...

'' have additional genes under the control of malT. In many

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. The Gram stain is ...

bacteria, such as ''

Streptococcus pneumoniae ''Streptococcus pneumoniae'', or pneumococcus, is a Gram-positive, spherical bacteria, hemolysis (microbiology), alpha-hemolytic member of the genus ''Streptococcus''. ''S. pneumoniae'' cells are usually found in pairs (diplococci) and do not f ...

'', maltose catabolism is regulated differently, via a transcriptional

repressor In molecular genetics, a repressor is a DNA- or RNA-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to the ...

called malR, in the

lac repressor Lac may refer to: Places Africa * Lac Region, a district in Chad * Lac Prefecture, a district in Chad America * Rivière du Lac, a tributary of the Montmorency River, in Capitale-Nationale, Quebec, Canada Europe * Laç, a city in Albania * Lac ...

family.

References

Bacterial genetics {{genetics-stub