Links between extracellular proteases, matrix components production and cell-cell communication in a Bacillus subtilis biofilm

doctoral dissertation

Mihael Špacapan (Author), Tjaša Danevčič (Mentor), Sonja Smole Možina (Thesis defence commission member), Matej Butala (Thesis defence commission member), Nicola R. Stanley-Wall (Thesis defence commission member), Ines Mandić-Mulec (Co-mentor)

Abstract

Po Gramu pozitivne bakterije uporabljajo peptide (autoinduktorje, AI) za medcelično komunikacijo, s katerimi lahko regulirajo številne prilagoditve na kritično celično gostoto populacije (kvorum). Obstoječe teorije in raziskave predpostavljajo, da AI signali in pripadajoči sistemi za zaznavanje kvoruma regulirajo sintezo javnih dobrin (npr. zunajceličnih proteaz in komponent matriksa, ki povezuje celice v biofilmih). To teorijo smo testirali tudi v okviru doktorske disertacije. Kot model smo uporabili komunikacijski sistem bakterije Bacillus subtilis, ki temelji na signalnem peptidu ComX in je del komunikacijskega sistema ComQXPA. Ta uravnava bakterijsko genetsko kompetenco in proizvodnjo lipopeptidnega antibiotika surfaktina sorazmerno s celično gostoto. Predpostavili smo, da imajo mutante, ki ne proizvajajo ComX, znižano proizvodnjo zunajceličnih proteaz in komponent matriksa. Prav tako smo preiskovali razgradnjo peptida ComX s strani zunajceličnih proteaz bakterije B. subtilis. Eksperimenti so potrdili pozitivno vlogo signala ComX pri proizvodnji zunajceličnih proteaz in občutljivost ComX za razgradnjo z zunajceličnimi proteazami, ki jih regulira. Vloga ComX pri sintezi komponent matriksa je bila v nasprotju s testirano hipotezo. V plavajočem biofilmu mutante ComX smo namreč izmerili višjo kumulativno izražanje promotorjev matriksa (P epsA , P tapA ); višjo koncentracijo zunajceličnih polisaharidov in proteinov na plavajoči biofilm, a tudi nižje izražanje sporulacijskega gena spoIIQ, nižje število spor in več celic na plavajoči biofilm kot pri divjem tipu. Zaključili smo, da sistem ComQXPA služi bakteriji kot »stikalo«, ki zmanjša energijski vložek bakterij v rast in razvoj biofilma in zagotovi večji vložek energije v sporulacijo in druge zgoraj omenjene adaptacije.

Keywords

cell signaling;protease;quorum quenching;biofilms;degredative enzymes;quorum sensing;pellicles;sporulation;

Data

Language:	English
Year of publishing:	2019
Typology:	2.08 - Doctoral Dissertation
Organization:	UL BF - Biotechnical Faculty
Publisher:	[M. Špacapan]
UDC:	602.3:579.852.11:579.22:579.25(043.3)
COBISS:	9334393
Views:	684
Downloads:	287
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary title:	Povezave med sintezo zunajceličnih proteaz, komponent matriksa in medcelično komunikacijo v biofilmu bakterije Bacillus subtilis
Secondary abstract:	Gram-positive bacteria use peptides as auto-inducing (AI) signals to regulate adaptive processes such as production of public goods (extracellular molecules that can be shared by the community). ComX is an AI peptide, mostly known for its role in the regulation of bacterial competence and surfactin production in Bacillus subtilis. These two traits are regulated accordingly to the bacterial population size, thus classifying ComX as a quorum sensing (QS) signal. We used this peptide-based AI system (the ComQXPA system), as a model to explore the links between cell-cell communication, exoprotease production and biofilm matrix production. The positive regulation of public goods (e.g. biofilm matrix components and exoproteases) by AI molecules in bacteria has been implied by several existing theories and experiments. In order to further corroborate these assumptions, we tested two hypotheses, predicting that the inactivation of the B. subtilis cell-cell communication system will have a negative impact on the production of exoproteases and biofilm matrix components. We also investigated the potential of ComX regulated proteases to degrade the ComX AI peptide. Obtained results confirmed that ComX plays an important role in exoprotease synthesis. Additionally, we confirmed that the ComX regulated exoproteases can degrade this signaling peptide. However, we also observed that the ComQXPA QS system slows down the overall production of biofilm matrix components and promotes sporulation. The floating biofilms of ComX deficient mutants produce more matrix components, more cells but less spores at an early stage of biofilm formation and exhibit a more synchronous induction into sporulation at the later stage. These results suggest that the ComQXPA QS system serves as a switch that down modulates investment into growth and biofilm formation and assures early investment into sporulation and aforementioned late growth adaptations.
Secondary keywords:	celično signaliziranje;proteaze;dušenje kvoruma;biofilm;razgradni encimi;zaznavanje kvoruma;plavajoči biofilm;sporulacija;Bacillus;
Type (COBISS):	Doctoral dissertation
Study programme:	0
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Biotehniška fak.
Pages:	XII, 99, [10] f.
ID:	11271318