Role of regulatory modules and small GTPases encoded by cvn operons in controlling growth of Streptomyces bacteria
(2025) MOBN03 20242Degree Projects in Molecular Biology
- Abstract
- Unlike most bacteria, Streptomyces grows by extending branching hyphae, forming a mycelium that resembles fungal growth more than typical prokaryotic behaviour. This growth strategy leads to questions about how bacteria control cell shape, polarity, and development in a multicellular context. While many regulatory systems involved in Streptomyces development have been described, others remain poorly understood. One such example is a group of conserved operons known as conservons (cvn), of which Streptomyces venezuelae has eight copies. However, their biological roles remain unclear. Flärdh’s lab has previously found that deleting cvn1 and cvn2 operons impacts cell shape and growth, leading to a phenotype characterised by hyphal bundling... (More)
- Unlike most bacteria, Streptomyces grows by extending branching hyphae, forming a mycelium that resembles fungal growth more than typical prokaryotic behaviour. This growth strategy leads to questions about how bacteria control cell shape, polarity, and development in a multicellular context. While many regulatory systems involved in Streptomyces development have been described, others remain poorly understood. One such example is a group of conserved operons known as conservons (cvn), of which Streptomyces venezuelae has eight copies. However, their biological roles remain unclear. Flärdh’s lab has previously found that deleting cvn1 and cvn2 operons impacts cell shape and growth, leading to a phenotype characterised by hyphal bundling and a clustered, disorganised growth pattern, when compared to the wild type. Each conservon consists of four genes, whose products likely work together as part of a signal transduction complex that detects environmental signals and activates the appropriate intracellular response. The aim of this project is to improve understanding of how the cvn1 and cvn2 operons regulate bacterial cell shape and growth in S. venezuelae, by clarifying the roles of the genes they encode. Here, we generated mutants lacking individual cvn1 and cvn2 genes and performed different complementation assays. The resulting phenotypes were examined and quantified using phase-contrast microscopy combined with Fiji-based image analysis. Our results revealed which genes are responsible for the bundling phenotype upon deletion of the whole operon. Furthermore, we found that there’s some degree of redundancy amongst the two operons. Finally, a bioinformatics approach, combined with site-directed mutagenesis and complementation tests, were used to successfully identify key residues in the CvnD2 GTPase, the protein encoded by the last gene of the cvn2 operon that functions as a molecular switch to regulate cellular processes. Further work will be needed to determine what stimuli the system responds to and the precise mechanism by which these proteins affect polar growth. (Less)
- Popular Abstract
- A Microscopic Tale: What Mechanisms Shape Bacteria?
When people think of bacteria, they often imagine harmful organisms that make us sick. But not all bacteria are bad – in fact, some are essential to life as we know it. One fascinating group is Streptomyces, a type of bacteria that live in the soil. They have an extraordinary ability to produce chemical compounds that kill other bacteria – antibiotics, making them extremely valuable for society. But their talents don’t stop there: unlike most bacteria, Streptomyces grow like fungi, forming branching filaments and even producing spores. In my thesis, I explore how the Streptomyces venezuelae species grows and what mechanisms shape its structure, aiming to better understand these special... (More) - A Microscopic Tale: What Mechanisms Shape Bacteria?
When people think of bacteria, they often imagine harmful organisms that make us sick. But not all bacteria are bad – in fact, some are essential to life as we know it. One fascinating group is Streptomyces, a type of bacteria that live in the soil. They have an extraordinary ability to produce chemical compounds that kill other bacteria – antibiotics, making them extremely valuable for society. But their talents don’t stop there: unlike most bacteria, Streptomyces grow like fungi, forming branching filaments and even producing spores. In my thesis, I explore how the Streptomyces venezuelae species grows and what mechanisms shape its structure, aiming to better understand these special microbes.
Genetic information refers to an organism’s hereditary material that encodes and influences several characteristics, which is stored in DNA. A gene is a segment of DNA that carries the information to make a protein – molecule that can influence how an organism grows and functions. In bacteria, the genes whose products (proteins) work together are organised into groups called operons.
Curiously, Streptomyces carry a set of conserved operons (also called conservons, cvn) – groups of genes found in multiple copies and across different species. Although their exact function is still unknown, the fact that they are well-preserved and repeated suggests they play an important role. Each of these cvn operons is composed of four genes: cvnA, cvnB, cvnC and cvnD. The protein CvnA is thought to sense external environmental signals and to communicate them to CvnD, which (with the help of CvnB) activates the appropriate intracellular response. The function of CvnC is unknown.
It was previously found in our lab that mutating two of the eight conservons found in S. venezuelae, namely cvn1 and cvn2, makes the bacterial shape change dramatically. As depicted in the figure, in the wild type bacteria (form found in nature) there is an organised structure in which the filaments grow almost as avoiding each other. In contrast, the morphology of the cvn1 and cvn2 mutants is characterised by filaments growing together in bundles. The main goal of this project is to mutate individual genes to better understand what roles these operons play in controlling cell shape and growth of S. venezuelae.
By analysing the results of mutating individual genes within the operons, our study revealed which specific genes are responsible for the bundling behaviour. We also discovered that cvn1 and cvn2 can partly take over each other’s biological functions. Using bioinformatics analysis along with genetic experiments, we identified key portions of the CvnD2, the protein encoded by the last gene of the cvn2 operon. This brings us closer to uncovering exactly how the protein works and contributes to the unique growth pattern of S. venezuelae. Further work is needed to discover what stimuli trigger this system and how the proteins exactly influence bacterial shape and growth.
Master’s Degree Project in Molecular Biology, 60 credits, 2025
Department of Biology, Lund University
Advisors: Klas Flärdh and Dima Massri
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9214743
- author
- Ramalhete Salvado Paz Louro, Sara
- supervisor
-
- Klas Flärdh LU
- Dima Massri LU
- organization
- course
- MOBN03 20242
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9214743
- date added to LUP
- 2025-10-31 16:35:50
- date last changed
- 2025-10-31 16:35:50
@misc{9214743,
abstract = {{Unlike most bacteria, Streptomyces grows by extending branching hyphae, forming a mycelium that resembles fungal growth more than typical prokaryotic behaviour. This growth strategy leads to questions about how bacteria control cell shape, polarity, and development in a multicellular context. While many regulatory systems involved in Streptomyces development have been described, others remain poorly understood. One such example is a group of conserved operons known as conservons (cvn), of which Streptomyces venezuelae has eight copies. However, their biological roles remain unclear. Flärdh’s lab has previously found that deleting cvn1 and cvn2 operons impacts cell shape and growth, leading to a phenotype characterised by hyphal bundling and a clustered, disorganised growth pattern, when compared to the wild type. Each conservon consists of four genes, whose products likely work together as part of a signal transduction complex that detects environmental signals and activates the appropriate intracellular response. The aim of this project is to improve understanding of how the cvn1 and cvn2 operons regulate bacterial cell shape and growth in S. venezuelae, by clarifying the roles of the genes they encode. Here, we generated mutants lacking individual cvn1 and cvn2 genes and performed different complementation assays. The resulting phenotypes were examined and quantified using phase-contrast microscopy combined with Fiji-based image analysis. Our results revealed which genes are responsible for the bundling phenotype upon deletion of the whole operon. Furthermore, we found that there’s some degree of redundancy amongst the two operons. Finally, a bioinformatics approach, combined with site-directed mutagenesis and complementation tests, were used to successfully identify key residues in the CvnD2 GTPase, the protein encoded by the last gene of the cvn2 operon that functions as a molecular switch to regulate cellular processes. Further work will be needed to determine what stimuli the system responds to and the precise mechanism by which these proteins affect polar growth.}},
author = {{Ramalhete Salvado Paz Louro, Sara}},
language = {{eng}},
note = {{Student Paper}},
title = {{Role of regulatory modules and small GTPases encoded by cvn operons in controlling growth of Streptomyces bacteria}},
year = {{2025}},
}