Hathaway, Lucy J. Meier, Patricia Stutzmann Bättig, Patrick Aebi, Suzanne Mühlemann, Kathrin <jats:title>ABSTRACT</jats:title> <jats:p>The epidemiology, phylogeny, and biology of nonencapsulated <jats:italic>Streptococcus pneumoniae</jats:italic> are largely unknown. Increased colonization capacity and transformability are, however, intriguing features of these pneumococci and play an important role. Twenty-seven nonencapsulated pneumococci were identified in a nationwide collection of 1,980 nasopharyngeal samples and 215 blood samples obtained between 1998 and 2002. On the basis of multilocus sequence typing and capsule region analysis we divided the nonencapsulated pneumococci into two groups. Group I was closely related to encapsulated strains. Group II had a clonal population structure, including two geographically widespread clones able to cause epidemic conjunctivitis and invasive diseases. Group II strains also carried a 1,959-bp homologue of <jats:italic>aliB</jats:italic> (<jats:italic>aliB-</jats:italic>like ORF 2) in the capsule region, which was highly homologous to a sequence in the capsule region of <jats:italic>Streptococcus mitis</jats:italic>. In addition, strains of the two major clones in group II had an additional sequence, <jats:italic>aliB-</jats:italic>like ORF 1 (1,968 to 2,004 bp), upstream of <jats:italic>aliB-</jats:italic>like ORF 2. Expression of <jats:italic>aliB-</jats:italic>like ORF 1 was detected by reverse transcription-PCR, and the corresponding RNA was visualized by Northern blotting. A gene fragment homologous to <jats:italic>capN</jats:italic> of serotypes 33 and 37 suggests that group II strains were derived from encapsulated pneumococci some time ago. Therefore, loss of capsule expression in vivo was found to be associated with the importation of one or two <jats:italic>aliB</jats:italic> homologues in some nonencapsulated pneumococci.</jats:p> application/pdf https://sonar.ch/global/documents/239893 eng info:eu-repo/semantics/altIdentifier/doi/10.1128/jb.186.12.3721-3729.2004 info:eu-repo/semantics/altIdentifier/issn/0021-9193 info:eu-repo/semantics/openAccess Journal of Bacteriology. - American Society for Microbiology. - 2004, vol. 186, no. 12, p. 3721-3729 Molecular Biology Microbiology A Homologue of aliB Is Found in the Capsule Region of Nonencapsulated Streptococcus pneumoniae http://purl.org/coar/resource_type/c_6501