| 1. |
- Jalalvand, Farshid, et al.
(författare)
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Protein domain-dependent vesiculation of Lipoprotein A, a protein that is important in cell wall synthesis and fitness of the human respiratory pathogen Haemophilus influenzae
- 2022
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Ingår i: Frontiers in cellular and infection microbiology. - : Frontiers Media SA. - 2235-2988. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- The human pathogen Haemophilus influenzae causes respiratory tract infections and is commonly associated with prolonged carriage in patients with chronic obstructive pulmonary disease. Production of outer membrane vesicles (OMVs) is a ubiquitous phenomenon observed in Gram-negative bacteria including H. influenzae. OMVs play an important role in various interactions with the human host; from neutralization of antibodies and complement activation to spread of antimicrobial resistance. Upon vesiculation certain proteins are found in OMVs and some proteins are retained at the cell membrane. The mechanism for this phenomenon is not fully elucidated. We employed mass spectrometry to study vesiculation and the fate of proteins in the outer membrane. Functional groups of proteins were differentially distributed on the cell surface and in OMVs. Despite its supposedly periplasmic and outer membrane location, we found that the peptidoglycan synthase-activator Lipoprotein A (LpoA) was accumulated in OMVs relative to membrane fractions. A mutant devoid of LpoA lost its fitness as revealed by growth and electron microscopy. Furthermore, high-pressure liquid chromatography disclosed a lower concentration (55%) of peptidoglycan in the LpoA-deficient H. influenzae compared to the parent wild type bacterium. Using an LpoA-mNeonGreen fusion protein and fluorescence microscopy, we observed that LpoA was enriched in “foci” in the cell envelope, and further located in the septum during cell division. To define the fate of LpoA, C-terminally truncated LpoA-variants were constructed, and we found that the LpoA C-terminal domain promoted optimal transportation to the OMVs as revealed by flow cytometry. Taken together, our study highlights the importance of LpoA for H. influenzae peptidoglycan biogenesis and provides novel insights into cell wall integrity and OMV production.
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| 2. |
- Ramesh, Malavika
(författare)
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Morphological changes in mycobacteria
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Morphological variations at different stages and conditions of growth has been observed frequently in various mycobacteria. Despite years of research, the molecular basis of such variations is still not clear and requires further elucidation. Owing to the pathogenic significance of mycobacteria, currently, mycobacterial research emphasizes on understanding responses to oxygen deprivation, starvation, various antibiotic treatments, latency and dormancy.In this thesis, change in cell shape from rod to coccoid, occurrence of refractive spore-like phase grey, phase bright bodies and branching are some of the morphological variations discussed. Further, this thesis also discusses microaerobic condition (oxygen deprivation) and the localisation pattern of the stressosome complex.
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| 3. |
- Riber, Leise, et al.
(författare)
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Hda-mediated inactivation of the DnaA protein and dnaA gene autoregulation act in concert to ensure homeostatic maintenance of the Escherichia coli chromosome
- 2006
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Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 20:15, s. 2121-2134
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Tidskriftsartikel (refereegranskat)abstract
- Initiation of DNA replication in Eschericia coli requires the ATP-bound form of the DnaA protein. The conversion of DnaA-ATP to DnaA-ADP is facilitated by a complex of DnaA, Hda (homologous to DnaA), and DNA-loaded beta-clamp proteins in a process termed RIDA (regulatory inactivation of DnaA). Hda-deficient cells initiate replication at each origin mainly once per cell cycle, and the rare reinitiation events never coincide with the end of the origin sequestration period. Therefore, RIDA is not the predominant mechanism to prevent immediate reinitiation from oriC. The cellular level of Hda correlated directly with dnaA gene expression such that Hda deficiency led to reduced dnaA gene expression, and overproduction of Hda led to DnaA overproduction. Hda-deficient cells were very sensitive to variations in the cellular level of DnaA, and DnaA overproduction led to uncontrolled initiation of replication from oriC, causing severe growth retardation or cell death. Based on these observations, we propose that both RIDA and dnaA gene autoregulation are required as homeostatic mechanisms to ensure that initiation of replication occurs at the same time relative to cell mass in each cell cycle.
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