Polar growth beyond Streptomyces: the life cycle of the marine bacterium Labrenzia aggregata

Harper, Stefan (2023) Polar growth beyond Streptomyces: the life cycle of the marine bacterium Labrenzia aggregata. Masters thesis, University of East Anglia.

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Abstract

Bacterial cell growth typically consists of cell extension and septum formation which leads to cell division. Enzymatic reactions breakdown the cell wall and allow for new cell wall synthesis leading to the growth and extension of the cell. The location of new cell wall synthesis, and therefore growth, is determined in bacteria by cytoskeletal proteins that scaffold the location of the enzymatic reactions. Labrenzia aggregata is a novel marine rod-shaped alpha-proteobacterium with importance in the production and degradation of the sulfur compound dimethylsulfoniopropionate, a key molecule in the global sulfur cycle. L. aggregata’s cell growth characteristics, however, have largely been ignored. In this work we have found that L. aggregata undergoes unipolar growth using fluorescent D-amino acids that establish the location of new cell wall synthesis. We hypothesised that the cytoskeletal protein behind the growth of this organism is ‘Lcy’ (Labrenzia cytoskeletal protein), a novel protein proposed to be a functional homologue of Scy. Scy is a key cytoskeletal polar growth protein of Streptomyces, in which Streptomyces is found in a different order to L. aggregata. Lcy was located at the same location as new cell wall synthesis and therefore growth, by using Lcy-Egfp. We established that lcy is likely an essential gene in L. aggregata as we could only generate a deletion mutation in the chromosome when lcy was supplied on a plasmid, induced with isopropyl β-D-1-thiogalactopyranoside (IPTG). Upon removal of IPTG the cells became rounded and lysed. Overexpression of Lcy in L. aggregata, controlled by an IPTG-inducible promoter, led to significant morphological changes in shape over time. New abnormal polarity centres formed, generating ‘Y’ or ‘T’ like shapes, which became more spherical at greater IPTG concentrations and over a longer time after IPTG addition. This work reveals greater insights into the understanding of bacterial polar growth, with L. aggregata being another example of how polar growth is becoming increasingly widespread in bacteria. Its mechanisms are highly important not just for fundamental cell biology but also for treatment to polar growing pathogenic bacteria such as Brucella, Bartonella and Mycobacterium species.

Item Type:	Thesis (Masters)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	11 Jun 2024 10:46
Last Modified:	11 Jun 2024 10:46
URI:	https://ueaeprints.uea.ac.uk/id/eprint/95567
DOI:

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