Explanation: The promoters also have conserved polyA and polyT tracts upstream of the -35 region. Some promoters also have a -16 region.

Explanation: E. coli ribosomes can support protein synthesis when directed by mRNA from a range of Gram-positive and Gram-negative organisms, whereas Ribosomes from B. subtilis recognize only homologous mRNA.

Explanation: Ribosomes from B. subtilis recognize only homologous MRNA. This is because they lack a counterpart of the largest E. coli Ribosomal protein.

Explanation: Few gram-positive bacteria such as staphylococcus, streptococcus, clostridium, and lactobacillus, lack S1-equivalent E.coli protein and therefore exhibit MRNA selectivity.

Explanation: The role of S1 is to bind RNA non-specifically and bring it to the decoding site of the 30S subunit, where proper positioning of the Shine-Dalgarno sequence and initiation codon signals can take place.

Explanation: The first controlled expression system to be used in B. subtilis was the Spac system, developed by Yansura and Henner in 1984.

Explanation: The first controlled expression system to be used in B. subtilis was the Spac system. This consists of the E. coli lacI gene and the promoter of phage SPO-1.

Explanation: The first controlled expression system to be used in B. subtilis was the Spac system. This consists of the E. coli lacI gene and the promoter of phage SPO-1.

Explanation: E. coli T7 system is implemented in B. subtilis by inserting the T7 RNA polymerase gene into the chromosome under the control of the Xylose-inducible promoter and cloning the gene of interest, coupled to T7 promoter, on a B. subtilis vector.

Explanation: E. coli T7 system is implemented in B. subtilis by inserting the T7 RNA polymerase gene into the chromosome under the control of the Xylose-inducible promoter and cloning the gene of interest, coupled to T7 promoter, on a B. subtilis vector.

Explanation: Expression of a heterologous gene in the T7 expression system can be made simpler by putting it directly under the control of the promoter.

Explanation: A xylose inducible system has also been developed in lactobacillus and staphylococci. Many different controllable promoters are available.

Explanation: In the phi-31 system of L. lactis, the gene of interest is placed under the control of a phage middle promoter inserted in a low copy number vector carrying the phage region ori.

Explanation: In the phi-31 system of L. lactis, the gene of interest is placed under the control of a phage middle promoter inserted in a low copy number vector carrying the phage region ori.

Explanation: Following infection of the host cell with phi-31, the plasmid copy number rapidly increases and this is followed by expression from the phage promoter.