to transfer among H. influenzae strands via conjugation. Likely protective role of transformation Unencapsulated H. influenzae is often observed in the airways of patients with chronic obstructive pulmonary disease (COPD). Neutrophils are also observed in large numbers in sputum from patients with COPD. The neutrophils phagocytize H. influenzae, thereby activating an oxidative respiratory burst. However instead of killing the bacteria the neutrophils are themselves killed (though such an oxidative burst likely causes DNA damage in the H. influenzae cells). Dearth of killing the bacteria appears to explain the persistence of infection in COPD. H. influenzae mutants defective in the rec1 gene (a homolog of recA) are very sensitive to killing by the oxidizing agent hydrogen peroxide. This finding suggests that rec1 expression is important for H. influenzae survival under conditions of oxidative stress. Since it is a homolog of recA, rec1 likely plays a key role in recombinational repair of DNA damage. Thus H. influenzae may protect its genome against the reactive oxygen species produced by the host's phagocytic cells through recombinational repair of oxidative DNA damages. Recombinational repair of a damaged site of a chromosome requires, in addition to rec1, a second homologous undamaged DNA molecule. Individual H. influenzae cells are capable of taking up homologous DNA from other cells by the process of transformation. Transformation in H. influenzae involves at least 15 gene products, and is likely an adaptation for repairing DNA damage in the resident chromosome. Vaccines that target unencapsulated H. influenzae serotypes are in development. See also Hattie Alexander Haemophilus influenzae cellulitis Haemophilus meningitis Maurice Hilleman Trimeric Autotransporter Adhesins (TAA) References External links Hib information on the World Health Organization (WHO) site. Fact sheet on the Centers for Disease Control and Prevention (CDC) site. Hib Initiative—from Johns Hopkins University, London School of Hygiene & Tropical Medicine, CDC & WHO November 2nd: World Pneumonia Day Website Type strain of Haemophilus influenzae at BacDive – the Bacterial Diversity Metadatabase Bacteria described in 1917 Gram-negative bacteria influenzae Pneumonia Capnophiles Polysaccharide encapsulated bacteria Vaccine-preventable diseases