Bacterial engineering

A process for producing a mutant bacterium which exhibits improved survival and/or growth under a selected growth condition, the process comprising the steps of:

• (a) generating a pool of mutant bacteria by transposon mutagenesis with an activating transposon (TnA), wherein the TnA comprises a promoter capable of increasing transcription of a gene at or near its insertion site;
• (b) growing bacteria from the mutant pool under the selected growth condition and under one or more reference conditions to produce two or more test cultures;
• (c) comparing the distribution of TnA insertions between test cultures to identify a first class of genes which are disadvantageous for growth and/or survival under the and/or survival under the selected growth condition and a second class of genes which are advantageous for growth and/or survival under the selected growth condition;
• and
• (d) providing an engineered mutant bacterium in which at least one of said disadvantageous genes is removed or disrupted and/or at least one of said advantageous gene is overexpressed, such that the mutant bacterium exhibits improved survival and/or growth under the selected growth condition.