Biology subjects

Cliff, J.

Publications and source records attributed to Cliff, J..

3 recordsLinked to original sources

bioRxiv2024

Comparing Raman and NanoSIMS for heavy water labeling of single cells

Stable isotope probing (SIP) experiments in conjunction with Raman microspectroscopy (Raman) or nano-scale secondary ion mass spectrometry (NanoSIMS) are frequently used to explore single cell metabolic activity in pure cultures as well as complex microbiomes. Despite the increasing popularity of these techniques, the comparability of isotope incorporation measurements using both Raman and NanoSIMS directly on the same cell remains largely unexplored. This knowledge gap creates uncertainty about the consistency of single-cell SIP data obtained independently from each method. Here, we conducted a comparative analysis of 543 Escherichia coli cells grown in M9 minimal medium in the absence or presence of heavy water (2H2O) using correlative Raman and NanoSIMS measurements to quantify the results between the two approaches. We demonstrate that Raman and NanoSIMS yield highly comparable measurements of 2H incorporation, with varying degrees of similarity based on the mass ratios analyzed using NanoSIMS. The 12C2H/12C1H and 12C22H/12C21H mass ratios provide targeted measurements of C-H bonds but may suffer from biases and background interference, while the 2H/1H ratio captures all hydrogen with lower detection limits, making it suitable for applications requiring comprehensive 2H quantification. Importantly, despite its higher mass resolution requirements, the use of C22H/C21H may be a viable alternative to using C2H/C1H due to lower background and higher overall count rates. Furthermore, using an empirical approach to determining Raman wavenumber ranges via the 2nd derivative improved the data equivalency of 2H quantification between Raman and NanoSIMS, highlighting its potential for enhancing cross-technique comparability. These findings provide a robust framework for leveraging both techniques, enabling informed experimental design and data interpretation. By enhancing cross-technique comparability, this work advances SIP methodologies for investigating microbial metabolism and interactions in diverse systems. ImportanceAccurate and reliable measurements of cellular properties are fundamental to understanding the function and activity of microbes. This study addresses to what extent Raman microspectroscopy and nano-scale secondary ion mass spectrometry (NanoSIMS) measurements of single cell anabolic activity can be compared. Here, we study the relationship of the incorporation of a stable isotope (2H through incorporation of 2H2O) as determined by the two techniques and calculate a correlation coefficient to support the use of either technique when analyzing cells incubated with 2H2O. The ability to discern between the comparative strengths and limitations of these techniques is invaluable in refining experimental protocols, enhancing data comparability between studies, data interpretation, and ultimately advancing the quality and reliability of outcomes in microbiome research.

microbiology↗

bioRxiv2023

Multicellular magnetotactic bacterial consortia are metabolically differentiated and not clonal

Consortia of multicellular magnetotactic bacteria (MMB) are currently the only known example of bacteria without a unicellular stage in their life cycle. Because of their recalcitrance to cultivation, most previous studies of MMB have been limited to microscopic observations. To study the biology of these unique organisms in more detail, we use multiple culture-independent approaches to analyze the genomics and physiology of MMB consortia at single cell resolution. We separately sequenced the metagenomes of 22 individual MMB consortia, representing eight new species, and quantified the genetic diversity within each MMB consortium. This revealed that, counter to conventional views, cells within MMB consortia are not clonal. Single consortia metagenomes were then used to reconstruct the species-specific metabolic potential and infer the physiological capabilities of MMB. To validate genomic predictions, we performed stable isotope probing (SIP) experiments and interrogated MMB consortia using fluorescence in situ hybridization (FISH) combined with nano-scale secondary ion mass spectrometry (NanoSIMS). By coupling FISH with bioorthogonal non-canonical amino acid tagging (BONCAT) we explored their in situ activity as well as variation of protein synthesis within cells. We demonstrate that MMB consortia are mixotrophic sulfate reducers and that they exhibit metabolic differentiation between individual cells, suggesting that MMB consortia are more complex than previously thought. These findings expand our understanding of MMB diversity, ecology, genomics, and physiology, as well as offer insights into the mechanisms underpinning the multicellular nature of their unique lifestyle. Significance statementThe emergence of multicellular lifeforms represents a pivotal milestone in Earths history, ushering in a new era of biological complexity. Because of the relative scarcity of multicellularity in the domains Bacteria and Archaea, research on the evolution of multicellularity has predominantly focused on eukaryotic model organisms. In this study, we explored the complexity of the only known bacteria without a unicellular stage in their life cycle, consortia of multicellular magnetotactic bacteria (MMB). Genomic and physiological analyses revealed that cells within individual MMB consortia are not clonal and exhibit metabolic differentiation. This implies a higher level of complexity than previously assumed for MMB consortia, prompting a reevaluation of the evolutionary factors that have led to the emergence of multicellularity. Because of their unique biology MMB consortia are ideally suited to become a model system to explore the underpinnings of bacterial multicellularity.

microbiology↗

bioRxiv2022

Correlative SIP-FISH-SEM-Raman-NanoSIMS links identity, morphology, biochemistry, and physiology of environmental microbes

Microscopic and spectroscopic techniques are commonly applied to study microbial cells but are typically used on separate samples, resulting in population-level datasets that are integrated across different cells with little spatial resolution. To address this shortcoming, we developed a workflow that correlates several microscopic and spectroscopic techniques to generate an in-depth analysis of individual cells. By combining stable isotope probing (SIP), fluorescence in situ hybridization (FISH), scanning electron microscopy (SEM), confocal Raman microspectroscopy (Raman), and nano-scale secondary ion mass spectrometry (NanoSIMS), we illustrate how individual cells can be thoroughly interrogated to obtain information about their taxonomic identity, structure, physiology, and metabolic activity. Analysis of an artificial microbial community demonstrated that our correlative approach was able to resolve the activity of single cells using heavy water SIP in conjunction with Raman and/or NanoSIMS and establish their taxonomy and morphology using FISH and SEM. This workflow was then applied to a sample of yet uncultured multicellular magnetotactic bacteria (MMB). In addition to establishing their identity and activity, backscatter electron microscopy (BSE), NanoSIMS, and energy-dispersive X-ray spectroscopy (EDS) were employed to characterize the magnetosomes within the cells. By integrating these techniques, we demonstrate a cohesive approach to thoroughly study environmental microbes on a single cell level.

microbiology↗