Bacterial transformation is the alteration of a bacterial cell's genotype and phenotype by the uptake of naked, foreign DNA from the surrounding environment. Small pieces of extracellular DNA are taken up by a living bacterium leading to a a stable change in the recipient cell. This process was thought to be rare. Now they've learned that many bacteria contains cell surface proteins that recognize and transport DNA from related species into the cell which then incorporates the foreign DNA into the genome.
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Transduction is when phages carry bacterial genes from one host cell to another as a result of aberrations in the phage reproductive cycle. General transduction moves random pieces of bacterial DNA as the phage lyses one cell and infects another during the lytic cycle. Some of the DNA can replace the homologous region of the recipient cell's chromosome only if a crossover takes place at both ends of the piece.
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