Table 2.

Characteristics of the Serum-Sensitive Mutants Identified in this Study

NMB NMA Number of mutants Gene Predicted function in databases S.I.
Capsule biosynthesis genes
 00691 siaB sialic acid biosynthesis protein9.20 10−2
 00703 siaA sialic acid biosynthesis protein<2.72 10−7
 007101981 ctrA capsule export outer-membrane protein9.36 10−3
 0072[iii] 01971 ctrB capsule export inner-membrane protein3.47 10−4
 007301961 ctrC capsule export inner-membrane protein<2.72 10−7
 007401952 ctrD capsule export ATP-binding protein8.34 10−3
 008201862 lipA capsule phospholipid modification protein<2.72 10−7
 008301855 lipB capsule phospholipid modification protein<2.72 10−7
 —1 — siaA-ctrAintergenic region3.66 10−4
LOS biosynthesis genes
 079010013 pgm phosphoglucomutase1.06 10−3
 082510341 rfaE ADP-heptose synthetase2.57 10−2
 082810372 rfaD ADP-L-glycero-d-manno-heptose epimerase1.39 10−1
 170419583 lgtF β-1,4-glucosyl transferase8.43 10−3
 192605271 IgtE latco-N-neotetraose biosynthesis glycosyl transferase9.00 10−3
 192905244 lgtA lacto-N-neotetraose biosynthesis glycosyl transferase3.07 10−2
 —[iv] 1 — region downstream lgtE 1.93 10−1
New genes
 00652hypothetical protein<2.72 10−7
 0352[iii] 21351possible sugar isomerase4.44 10−3
 063808481 galU probable UTP-glucose-1-phosphate uridylyltransferase1.65 10−2
 207603561possible transferase (aut family)8.99 10−3

[i] NMA and NMB denote the ORFs, in Z2491 and MC58 genomes, respectively, homologous to the sequence flanking the transposon insertion sites. Number of mutants indicates the number of insertions within a defined gene.

[ii] S.I., Survival index defined as the ratio of the number of CFU of mutant to wild type after 5 h in native serum (n = 3).

[iii] The transposon was inserted in the promoter region of the gene.

[iv] This mutant presented a truncated LOS, but the affected gene could not be identified using the available sequences.