Project description:Using RNA-Seq analysis we compared the transcriptome of Methylosinus trichosporium OB3b grown in the presence of varying amounts of copper and cerium. When copper was added in the absence of cerium, expression of genes encoding for both soluble and particulate methane monooxygenases varied as expected. Genes encoding for copper uptake, storage, and efflux also increased, indicating that methanotrophs must carefully control copper homeostasis. When cerium was added in the absence of copper, expression of genes encoding for alternative methanol dehydrogenases varied as expected, but few other genes were found have differential expression. When cerium concentrations were varied in the presence of copper, few genes were found to be either up or downregulated, indicating that copper over rules any regulation by cerium. When copper was added in the presence of cerium, however, many genes were upregulated, most notably multiple steps of the central methane oxidation pathway, the serine cycle, and the ethylmalonyl-CoA pathway. Many genes were also downregulated, including those encoding for nitrogenase and hydrogenase.
Project description:This study investigates the combined effects of copper availability and carbon source (methane versus methanol) on the physiology and transcriptome of Methylosinus trichosporium OB3b, a model Type II methanotroph. Methanotrophs oxidize methane to carbon dioxide through intermediates such as methanol, formaldehyde, and formate, using two forms of methane monooxygenase (MMO): the copper-dependent particulate MMO (pMMO) and the soluble MMO (sMMO). Although Msn. trichosporium OB3b can utilize both methane and methanol as sole carbon sources, growth on methanol is significantly affected by copper. In the presence of copper, methanol-grown cells exhibited impaired growth, formate accumulation, and decreased pH, while buffering with MOPS restored growth. NADH/NAD ratios increased nearly tenfold in methanol-grown cultures with copper, indicating redox imbalance. Transmission electron microscopy revealed disrupted intracytoplasmic membranes under these conditions. Transcriptomic analysis showed that genes involved in methanol oxidation were differentially expressed in response to copper and carbon source, and two siderophore biosynthetic gene clusters were repressed during methanol growth with copper. Overall, the findings suggest that Msn. trichosporium OB3b modulates metallophore expression and carbon metabolism to manage oxidative and redox stress under methanol growth conditions. Understanding these regulatory mechanisms is critical for optimizing methanotroph-based biotechnological applications, including methanol-driven biosynthesis of valuable compounds such as methanobactin.
Project description:Methane oxidation by aerobic methanotrophs is well-known to be strongly regulated by the availability of copper, i.e., the “copper-switch”. That is, there are two forms of the methane monooxygenase: a cytoplasmic or soluble methane monooxygenase (sMMO) and a membrane-bound or particulate methane monooxygenase (pMMO). sMMO is only expressed and active in the absence of copper, while pMMO requires copper. Previous work has also shown that one gene in the operon of the soluble methane monooxygenase – mmoD – also plays a critical role, but its function is still vague. Herein we show that MmoD is not needed for expression of genes in the sMMO gene cluster but is critical for formation of sMMO polypeptides and sMMO activity in Methylosinus trichosporium OB3b, indicating that MmoD plays a key post-transcriptional role in maturation of sMMO. Further, data also show that MmoD controls expression of methanobactin, a unique copper-binding compound used by some methanotrophs for copper collection. Collectively these results provide greater insights into the components of the “copper-switch” and thus provide new strategies to manipulate methanotrophic activity.
Project description:W614A-3S peptide is a modified 3S motif of the HIV-gp41 (mutation W614A). We previously detected the presence of natural neutralizing antibodies directed against W614A-3S peptide (NAbs) in long-term non-progressor HIV+ patients. Here, we compared the efficacy of W614A-3S peptide formulated in either squalene emulsion (SQE) or in aluminum hydroxide (Alum) in inducing broadly-NAbs (bNAbs). Rabbit and mouse models were used to screen the induction of bNAbs following 4 immunizations. SQE was more efficient than Alum formulation in inducing W614A-3S-specific bNAbs with up to 67-93% of HIV strains neutralized. We then analyzed the quality of peptide-specific murine B cells by single-cell gene expression by quantitative Reverse Transcription-PCR and single-cell V(D)J sequencing. We found more frequent germinal center B cells in SQE than in Alum, albeit with a different gene expression profile. The V(D)J sequencing of W614A-3S-specific BCR showed significant differences in BCR sequences and validates the dichotomy between adjuvant formulations. All sixteen BCR sequences which were cloned were specific of peptide. Adjuvant formulations of W614A-3S-peptide-conjugated immunogen impact the quantity and quality of B cell immune responses at both the gene expression level and BCR sequence. We used a single-cell quantitative Reverse Transcription-PCR (qRT-PCR) approach to compare between the two formulations the quality of W614A-3S-specific B cell populations isolated from draining lymph nodes, one week after 2nd and 3rd immunizations (W3 and W5, respectively).