Biology subjects

Gangan, M. S.

Publications and source records attributed to Gangan, M. S..

5 recordsLinked to original sources

bioRxiv2026

3D bioprinting of engineered living materials in support slurries for complex free-standing structures

The combination of synthetic biology and additive manufacturing has driven major changes in production of biomaterials, especially through the use of three-dimensional (3D) bioprinting to create engineered living materials. However, current fabrication methods can be limited by prohibitive hardware costs and the inability to maintain structural fidelity in complex, free-form living architectures. This work demonstrates how to build a low-cost, open-source 3D bioprinting platform that can make complicated bacterial structures with complex geometry and high dimensional accuracy. A commercially available, conventional fused deposition modeling 3D printer was modified to create a bioprinting system that is simple to build. The modified bioprinter, which costs around $450, is less expensive than many commercial bioprinters. This 3D-printing technology uses slurry-based support bath methods featuring low-cost gelatin and agarose microparticles, resulting in structures with a high aspect ratio (>8:1) and feature sizes as small as 260 m. The optimization of critical printing settings, including the ability of the bioink to retract during non-print movements, resulted in a reduction of unwanted bacterial deposition by nearly two orders of magnitude. Long-term viability experiments showed that bacteria in the bioprints could survive for at least 28 days with nutrient supplementation. Additionally, 3D-printed engineered biofilms revealed that incubation conditions and extracellular matrix composition significantly impacted the mechanical properties of printed constructs, with tradeoffs between matrix production and mechanical integrity. This study showcases an accessible 3D bioprinting platform for advanced bioprinting technologies, enabling development of engineered living materials with potential applications in synthetic biology, biotechnology, and tissue engineering.

synthetic biology↗

bioRxiv2025

3D-bioprinted marine bacteria for the degradation of bioplastics

The severe, long-lasting harm caused by plastic pollution to marine ecosystems and coastal economies has led to the development of biodegradable plastics; however, their limited decomposition in cold, dark marine environments remains a challenge. Here, we present our newly developed technologies for creating 3D-bioprinted living materials for bioplastic degradation with specific use in marine environments. Our approach integrates halotolerant bioplastic-degrading bacterium Bacillus sp. NRRL B-14911 into alginate-based bio-ink to print an engineered living material (ELM) termed a "bio-sticker." Quantification of bacteria viability reveals that bioprinted marine bacteria survive within bio-stickers for more than three weeks. The rate at which the bio-stickers degrade the bioplastic polyhydroxybutyrate (PHB) can be tuned by altering bio-sticker biomass concentration, bioplastic concentration, or incubation temperature. Bio-stickers that are transferred to a new PHB sample still retain high biodegradation activity, demonstrating their durability. Strain sweep oscillatory tests demonstrate viscoelastic behavior of the bio-stickers. Monotonic tensile tests indicate that the elastic modulus and the adhesion of the bio-stickers are not negatively impacted by bacteria growth or incubation temperature. Our work paves the way for development of ELMs to facilitate the inclusion of bioplastics within the blue economy, promoting the emergence of more sustainable and eco-friendly materials.

synthetic biology↗

bioRxiv2022

Bacterial produce membrane-binding small molecules to regulate horizontal gene transfer in vesicles

The exchange of bacterial extracellular vesicles facilitates molecular exchange between cells, including the horizontal transfer of genetic material. Given the implications of such transfer events on cell physiology and adaptation, some bacterial cells have likely evolved mechanisms to regulate vesicle exchange. Past work has identified mechanisms that regulate the formation of extracellular vesicles, including the production of small molecules that modulate membrane structure, however whether these mechanisms also regulate vesicle uptake and have an overall impact on the rate of vesicle exchange is unknown. Here we show that membrane-binding molecules produced by microbes regulate both the formation and uptake of extracellular vesicles and have the overall impact of increasing the vesicle exchange rate within a bacterial coculture. In effect, production of compounds that influence vesicle exchange rates enable cells to steal genes from neighboring cells. The ability of several membrane-binding compounds to regulate vesicle exchange was demonstrated. Three of these compounds, nisin, colistin, and polymyxin B, are antimicrobial peptides added at sub-inhibitory concentrations. These results suggest that a key function of exogenous compounds that bind to membranes may be the regulation of vesicle exchange between cells. ImportanceThe exchange of bacterial extracellular vesicles is one route of gene transfer between bacteria, although it was unclear if bacteria developed strategies to regulate the rate of gene transfer within vesicles. In eukaryotes, there are many examples of specialized molecules that have evolved to facilitate the production, loading, and uptake of vesicles. Recent work with bacteria has shown that some small molecules influence membrane curvature and induce vesicle formation. Here we show that similar compounds facilitate vesicle uptake, thereby regulating the overall rate of vesicle exchange within bacterial populations. The addition of membrane-binding compounds, several of them antibiotics at sub-inhibitory concentrations, to a bacterial co-culture increased the rate of horizontal gene transfer via vesicle exchange.

microbiology↗

bioRxiv2021

Optimal strategy for public good production is set by balancing intertemporal trade-off between population growth rate and carrying capacity

Public goods are biomolecules that contribute to the community welfare. Their production can benefit populations in many ways, such as by providing access to previously unutilized resources. However, public good production has often been energetically costly, resulting in a reduction in the cellular growth rate. To reduce this cost, populations have evolved strategies to regulate biosynthesis of public good. Among these cell densities dependent regulation of public goods, as accomplished by quorum sensing, is a widely studied mechanism. Given that the fitness costs and benefits of public good production must be balanced, adoption of quorum sensing as a regulatory pathway by bacterial cells may have parallels with several economic principles that are used to study optimal investment decisions. Here, we explore the regulation of a public good, whose benefit is an increase in the carrying capacity, through experimental measurements of growth for engineered strains of Escherichia coli and analysis of those results using a modified logistic growth model. By varying the cell density at which the production of the public good was activated, we showed sharply-peaked optimum population fitness. Analysis further revealed that cell density associated with maximum public good benefits was determined by the trade-off between the cost of public good production, in terms of reduced growth rate, and benefits received from public good, in the form of increased carrying capacity. Moreover, our model showed that cells with luxRI quorum sensing seem to upregulate public good expression when the benefits from the production was immediate. These results demonstrate a case where a biological system apparently has evolved to optimize the timing of public good production to account for short-term costs and delays in reaping a future benefit. Author summaryBacteria often cooperate by sharing resources, sometimes referred as public goods. The activity of public good molecules benefits all of the neighboring cells. Here we examine the public good amylase, an enzyme to break down starch into smaller pieces that can be eaten by cells. Amylase production benefits the entire population because it enables growth to a larger population size, but production of this enzyme also has a cost. Enzyme production requires cells to expend energy and cellular resources. To balance the cost and benefit of the production of amylase, cells have likely evolved a strategy to control the timing of the production of public goods. We tested the dependence of population fitness on the timing of amylase production, finding an optimal cell density for amylase production. Finding the balance means that cells have evolved to anticipate future events, such as when simple food sources are depleted. Similar balancing of immediate costs and future benefits has been observed and studied in economics. Our results revealed that cells which use the regulatory strategy quorum sensing to control amylase production have minimized the delay in obtaining a benefit from this public good.

microbiology↗

bioRxiv2019

Asymmetric Cell Growth and Nucleoid Displacement in Escherichia coli

Single celled growth of Escherichia coli is typically considered as an example symmetric division, based on the sizes of daughter cells and precision of center finding of the septum. Here, we investigate the symmetry of membrane addition in the mid-plane and DNA segregation using a video-microscopy approach. We find the membrane expansion dynamics to be asymmetric based on mid-cell photobleaching landmarks in FM4-64, used to stain the membrane. The apparent growth bias of E. coli does not correspond to the age of the pole. We find the membrane growth asymmetry is correlated to nucleoid displacement, consistent with ideas of coupling of cell growth and nucleoid positioning. The mobility of the actin-homolog MreB also correlates with membrane growth asymmetry, based on fluorescence recovery after photobleaching (FRAP) measurements of a YFP-fusion. These correlations suggest the small asymmetry of membrane addition observed could potentially drive nucleoid segregation and MreB mobility asymmetry in E. coli.\n\nIMPORTANCEAsymmetry in bacterial cell division is seen in its most simple form in the binomial event of protein segregation that results in noise in equal segregation and depends on the protein copy number. In the case of specific proteins this can also affect growth, and result in differentiation. However, during the asexual division of Escherichia coli single cells are thought to grow symmetrically and divide equally. We find a slight but consistent asymmetry in growth based on quantitative morphometry of cell pole displacement in time-series of growing E. coli cells. Increased cell wall extension in one half of the cell over the other appears to explain the asymmetry in the displacement of cell poles. Interestingly the growth asymmetry is not correlated to the age of the pole (old and new). This observed asymmetry appears to correlate with the asymmetry of nucleoid segregation, resulting in the nucleoids finding the midpoints of the respective daughter cells, and formation of the septum at the geometric centre of the elongated cell just prior to division. The mobility dynamics of the cytoskeletal protein MreB, which organizes the cell membrane, is are more dynamic where membrane growth is faster. Thus we propose a linkage between this observed growth asymmetry and that of MreB dynamics.

microbiology↗