setting up and estimating the pellicle biofilm development in mycobacterium smegmatis cultures

Developing and Assessing Pellicle Biofilms in Mycobacteria

Bacteria are able to survive as single-celled entities; however, in most physiologically relevant conditions, they organize into community mimetics. Biofilm is a widely recognized community organization of bacteria formed by aggregated cells encased in a self-produced matrix1. Such assembly possesses signatures of early multicellularity and provides higher stress resilience to bacterial systems. Biofilms are often tolerant to antimicrobials and are estimated to be responsible for almost 80% of microbial infections2,3.
Shake flask and plate-based cultures have traditionally been the usual practices for bacterial culturing. Their enormous acceptability and success can be attributed to their ease of handling, reproducibility, and scalability. However, the lack of physiological context limits the translational potential of the knowledge generated using such systems4. Therefore, biofilms are becoming an attractive model system to study bacterial pathophysiology. Biofilms provide a dynamic model system, closely mirroring natural conditions, allowing researchers to replicate physiological aspects such as nutrient gradients and spatial heterogeneity5,6.
The biofilm lifestyle is particularly pertinent in mycobacterial studies, as mycobacteria, including the notorious Mycobacterium tuberculosis, are adept biofilm formers7. Their ability to thrive within biofilms contributes to their persistence in host tissues during infections. It poses a formidable challenge in treating mycobacterial diseases, given the inherent antibiotic resistance associated with biofilm lifestyles8. Biofilms also provide an ideal model system to study mycobacterial metabolism, as they allow for the investigation of the unique metabolic adaptations and nutrient utilization strategies employed by mycobacteria within complex microbial communities9.
While biofilm is increasingly being accepted as a better model system for mycobacterial studies10, there is a need for consistent and reproducible standard operating procedures, especially for drawing parallels among studies conducted in different laboratories. The method outlined here describes biofilm formation procedures for a mycobacterial species, M. smegmatis. M. smegmatis is a more accessible model for studying mycobacterial biofilms, given its non-pathogenicity and faster biofilm formation kinetics. The method can be modified to suit applications like antimycobacterial screening, metabolite extraction, and omics studies.

Author Spotlight: Advancing Mycobacterial Biofilm Protocols for Enhanced Bacterial Metabolism Research

Growing Mycobacterial Biofilm as a Model to Study Antimicrobial Resistance

Our research focuses on bacterial metabolism, especially energy metabolism, which is crucial for growth and survival. Despite extensive biochemical and structural data, systems level understanding and adaptive mechanisms remain unclear. We aim to deepen this knowledge and to address antimicrobial resistance.Our protocol enhances the physiological relevance of lab experiments by using biofilms, which mimics the natural bacterial growth better than the planktonic methods. Adapting microbacterial biofilms will offer a great system to understand the gene's lifestyle, and it'll also offer a screening system for antimicrobials. We are not the first ones to produce mycobacterial biofilms.There are several groups using this as a model. Our motivation behind producing this protocol was to simplify the procedures as much as possible so many labs can adapt this system as a model.

Setting Up and Estimating the Pellicle Biofilm Development in Mycobacterium smegmatis Cultures

To begin, in a laminar hood, dispense six milliliters of Soutan's media supplemented with 2%glucose into the wells of a six-well plate. Inoculate the wells with 120 microliters of the secondary cultures of mycobacterium smegmatis. Keep one un-inoculated well as a media control.Next, pipette the culture up and down with a 1-milliliter micropipette for even mixing. Cover the lid and carefully seal the plate with paraffin film. Incubate the plate in a static incubator at 37 degrees Celsius for seven days.For a visual estimation of biofilm growth, place the plates in a gel documentation system under epi white light illumination. To measure dry weight, weigh a sheet of blotting paper. Extract the biofilm from the six-well plate and transfer it onto the paper with a spatula.Carefully collect most of the biofilm from the culture. Place the biofilm on the blotting paper. Place the blotting paper in an incubator until the biofilm dries completely.Then measure the combined weight of the paper and biofilm. Biofilm pellicles were visible from Day 3 onwards. Reticulation of the cultures improved with the addition of 2%glucose to Soutan's media.Biofilm development was visible between days 3 to 6. A film with slight reticulation was observed on Day 3. This film matured by Day 5 and disintegrated from Day 6.

Research

JoVE Journal

Biology

Many bacteria thrive in intricate natural communities, exhibiting key attributes of multicellularity such as communication, cooperation, and competition. ...