How iron and manganese affect the central metabolism in pathogenic mycobacteria

Project Information

Myco_Metabolism

Grant agreement ID: 101029081

DOI

10.3030/101029081

Project closed

EC signature date 23 April 2021

Start date 15 June 2021

End date 14 June 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 171 473,28

EU contribution

€ 171 473,28

Coordinated by

UNIVERSITA DEGLI STUDI DI PADOVA
Italy

Periodic Reporting for period 1 - Myco_Metabolism (How iron and manganese affect the central metabolism in pathogenic mycobacteria)

Reporting period: 2021-06-15 to 2023-06-14

Summary of the context and overall objectives of the project

Altering the availability of nutrients to starve or intoxicate pathogenic bacteria is one of the mechanisms our immune system uses to limit their replication or kill them. These nutrients include metals, elements that are essential for all cellular processes and whose intracellular concentration must be strictly controlled. Bacteria respond to these changes with specific mechanisms that allow them to survive.
This project investigated the effects of iron deficiency and high manganese concentrations on the metabolism of Mycobacterium tuberculosis and Mycobacterium abscessus, two unicellular pathogenic organisms that cause lung infections. This study reveals new aspects of the physiology of two pathogenic bacteria that are highly tolerant to antibiotics. Infections caused by M. tuberculosis and M. abscessus are difficult to treat precisely because of this high tolerance. Treatment lasts from six months to two years, and is accompanied by the obvious side effects of the drugs due to the extensive therapy. M. abscessus is of a particular clinical concern as it is more tolerant than M. tuberculosis. While there are international guidelines from the WHO for the latter, M. abscessus infections are dealt with on a case-by-case basis. The nutritional conditions used in this research define a metabolic state of the bacterial cell that has never before been used to study antibiotic resistance. Such conditions may provide a new screening platform to identify new drugs or to improve existing therapies, and are applicable to all pathogenic microorganisms, not just mycobacteria.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The work started with testing the growth of pathogenic bacteria in different combination of metals and energy sources in different concentration. The aim was to identify inhibitory or synergistic effects of specific metal concentrations on bacteria in specific physiological states induced by the presence of specific energy sources in the culture broth. The most interesting growth conditions were therefore selected for detailed analysis of the metabolic or physiological alterations. Gene expression, metabolic and proteomic analyses were performed. Under iron deficiency, clear and specific metabolic alterations were identified in M. tuberculosis revealing its adaptation mechanisms. A global physiological analysis was performed on M. abscessus exposed to sub-inhibitory concentrations of manganese in different metabolic states generated by feeding the bacterium with different energy sources. In this case, no specific changes of the central metabolism were identified, but alterations related to the translation apparatus were clear. This project reveals new aspects of the physiology of two pathogenic bacteria that are highly tolerant to antibiotics.
The results of this project were presented in two international conferences focused on mycobacterial research EMBO Workshop on Tuberculosis 2022 (12th-16th September 2022, Paris, France) and 42nd European Society of Mycobacteriology Congress 2022 (26th-29th June, Bologna, Italy).

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The subject of this project is a complex aspect of microbial physiology, the interaction between two cellular processes, metal homeostasis and central metabolism. These two processes are usually studied separately, and although obvious, their interaction is little explored in mycobacteria and bacteria more generally.
This project paved the way for understanding the mechanisms of adaptation of highly antibiotic-tolerant bacteria, such as Mycobacterium tuberculosis and Mycobacterium abscessus, to changes in metal availability in different metabolic states.
In this project, it was seen that specific alterations in energy metabolism occur in response to iron deficiency. No specific alterations in central metabolism in response to exposure to sub-inhibitory concentrations of manganese were identified, but alterations related to the translation apparatus were clear.
The nutritional conditions used in this research define a metabolic state of the bacterial cell that has never before been used for antibiotic resistance investigations. Such conditions may provide a new screening platform to identify new drugs or to improve existing therapies, and is applicable to all pathogenic microorganisms, not just mycobacteria. Given the spread of antibiotic resistance, the development of new medicines is urgently needed. And given the functional relevance of metabolism in mediating antibiotic resistance, diversifying screening programmes to test drugs (i.e. compound libraries) on bacteria in differentiated metabolic states defined by two nutrient variants, such as metal ion and carbon source, could represent a valid new way to develop novel antibacterial treatments.

Schematic representation of the scientific meaning of this study