title: The essentiality and involvement of Streptococcus intermedius histone-like DNA-binding protein in bacterial viability and normal growth.
abstract: Streptococcus intermedius histone-like DNA-binding protein (Si-HLP) is a homodimeric protein and, conserved with Escherichia coli HU, a well-documented nucleoid-associated protein (NAP). In E. coli, HU plays important roles as both structural and regulatory factors, but it is not essential for E. coli viability. Streptococcal HLP has been found to bind host cells and induce cytokine production, but its physiological role remains poorly defined. In the present study, using gene insertion knockout and tetracycline-regulated antisense RNA expression techniques, we determined whether Si-HLP is essential for bacterial viability and normal growth in S. intermedius. The Si-HLP-downregulated S. intermedius strain showed alterations in its morphology and surface properties. Downregulation of Si-HLP led to an expanded nucleoid to fill the intracellular space. Transcription levels of several genes, including virulence-associated factors, were found to be activated or repressed in the antisense Si-hlp RNA-expressing strain by real-time PCR and reverse-transcription PCR. Collectively, these data suggest that Si-HLP serves as an essential NAP governing the nucleoid architecture and controlling the gene transcription profile in S. intermedius.
authors.affiliation: Department of Microbiology, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kumamoto-cho, Tokushima 770-8504, Japan.
authors.forename: Dali
authors.initials: D
authors.lastname: Liu
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Yumoto
authors.forename: Keiji
authors.initials: K
authors.lastname: Murakami
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Hirota
authors.forename: Tsuneko
authors.initials: T
authors.lastname: Ono
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nagamune
authors.forename: Shizuo
authors.initials: S
authors.lastname: Kayama
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsuo
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Miyake
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006657:Histones; D050296:Microbial Viability; D034367:Streptococcus intermedius / Q000235:genetics / Q000254:growth & development* / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; D006657:Histones