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Daike, Temiloluwa (2024) QsrB mediated repression of quorum sensing in Clostridium acetobutylicum ATCC 824. PhD thesis, University of Nottingham.

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Abstract

The Gram-positive obligate anaerobe Clostridium acetobutylicum is

recognised for its ability to metabolise sugars into organic acids and

solvents, particularly the biofuel butanol. It is also a model organism for

clostridial spore formation, controlled by the master regulator Spo0A.

C. acetobutylicum has been historically used for industrial-scale

production of organic solvents like acetone and butanol however

improvements are required for a viable economic process. Signalling

peptide-based regulation of solvent formation and sporulation in

C. acetobutylicum ATCC 824 has been recognised and a regulatory role

for the RRNPP-type Quorum sensing system B (QssB) comprising

Quorum sensing regulator B (QsrB) and its cognate signalling peptide

Quorum sensing peptide B (QspB) has been established.

The aims of this PhD study were threefold: (i) to establish diversity and

distribution of RRNPP-type systems in the genus Clostridium, and in

particular those similar to QssB; (ii) to better understand how QssB

interlinks with the known Spo0A regulatory network and to establish

which genes it controls; and (iii) establish the sequence of the mature

QspB-derived signalling peptide.

Using a bioinformatics approach, RRNPP-type quorum sensing systems

were identified in 15 clostridial species and 112 strains in this category,

accounting for approximately 25% of the currently sequenced species of

the genus Clostridium sensu stricto. Of these, only 2 species and 16

strains contained a close homolog of the QssB system.

A transcriptomic comparison was undertaken between the

C. acetobutylicum ATCC 824 WT and its qsrB overexpressing derivative.

The latter had previously been shown to be considerably reduced in

solvent and endospore formation, a phenotype that was reproduced here

before RNA sequencing analysis commenced. The study

transcriptomically validated the observed phenotype of reduced solvent

formation and sporulation with a downregulation in genes involved in

solvent formation - adhE1, ctfA and ctfB. Noteworthy was the discovery

that despite the reduction in spore formation by the overexpression of

qsrB, QsrB did not appear to directly regulate the expression of spo0A

but rather reduced the expression of sporulation-specific sigma factors

and other genes controlled by Spo0A.

RRNPP-type quorum sensing peptides of the Qss system of

C. acetobutylicum were experimentally identified in culture supernatant

in this study. 6 heptapeptides deriving from the C-terminal part of

previously predicted C. acetobutylicum quorum sensing peptides could

be identified in spent culture supernatants. For QssB it was confirmed

that the QspB-derived mature signalling peptide consists of the sequence

AEPTWGW.

Future work may focus on establishing direct target genes for the QssB

system, precise mode of action, as well as establishing the proteases and

transporters involved in peptide maturation and uptake.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Winzer, Klaus Atkinson, Steve
Keywords:	Clostridium acetobutylicum, quorum sensing, ABE fermentation, QsrB, QspB, signalling peptides
Subjects:	Q Science > QR Microbiology > QR 75 Bacteria. Cyanobacteria
Faculties/Schools:	UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID:	77193
Depositing User:	Daike, Temiloluwa
Date Deposited:	19 Jul 2024 07:52
Last Modified:	19 Jul 2024 07:52
URI:	https://eprints.nottingham.ac.uk/id/eprint/77193

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