PubMed · 1245401
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
T J Lenehan, J F Greally. 1976-01-17. Neutrophil function--part II.. https://pubmed.ncbi.nlm.nih.gov/1245401/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The dissemination of antibiotic resistance genes (ARGs) in wastewater environments poses a severe threat to public health. Extracellular ARGs (eARGs) persist as free DNA fragments that are refractory to efficient removal by conventional physicochemical treatment technologies. Here, we isolated Stutzerimonas stutzeri CHY07 from municipal sewage and demonstrated that extracellular DNA fragments, including eARGs, can serve as chemoattractants for environmental bacteria. Through genomic mining, molecular docking, surface plasmon resonance (SPR), isothermal titration calorimetry (ITC) and protein-ligand interaction profiling, we identified the chemoreceptor Mcp16 as the primary sensor of extracellular DNA and revealed that it achieves sequence-independent recognition of the DNA phosphate backbone. We further established the endogenous pentapeptide VRSVR as a methylation substrate for CheR and constructed the engineered strain CHY07-2 (mcp16::VRSVR) using an SSB/CRISPR-Cas9 ribonucleoprotein (RNP) system. This strain exhibited significantly enhanced chemotactic responsiveness, achieving 72-h removal efficiencies of 96.56% and 91.60% for low- and high-molecular-weight eARGs in non-sterile WWTP secondary effluent; conversely, mcp16 deletion markedly attenuated both chemotaxis and removal, whereas in situ complementation restored them. These findings reveal a "chemotaxis-contact-removal" cascade - with a proposed self-reinforcing loop - in eARG-removing bacteria, providing both a theoretical framework and a technical paradigm for enhancing pollutant removal through targeted amplification of microbial chemotaxis.
An assay was developed which identifies individual bacterial tumbles and so allows rapid, quantitative measurements of tumble frequency in free-swimming bacteria. Tumble frequency is modulated by cells to enable chemotaxis. Mutations in the chemotaxis signal transduction pathway typically have phenotypes of altered tumble frequency. The purpose of this assay is to quantitatively measure steady-state tumble frequency to enable comparisons of mutant strain phenotypes. It was developed using Escherichia coli but should be applicable to other species with a peritrichous flagellation pattern, such as Salmonella typhimurium. Tumbles are defined by a combination of the parameters rate of change of direction and swimming speed, with a rapid change of direction defining the beginning of a tumble and increased swimming speed defining the end. These parameters have previously been shown to be correlated with tumbles in general but not used to identify discrete tumble events. The computer assay was validated by comparing its results with manual observations by eye. The assay was intended to be most sensitive to swimming patterns similar to wild type so as to resolve subtle changes which would result from partial-function mutations. It quantitatively detects extreme behavioral phenotypes as well and can be modified to increase resolution at either extreme if necessary.
Cyanobacteria have had a profound and unparalleled biogeochemical impact on the earth's biosphere. As the first oxygenic phototrophs, cyanobacteria were responsible for the transition from anaerobic to aerobic life. Ironically, molecular oxygen (O2) is inhibitory to critical components of cyanobacterial metabolism, including photosynthesis and nitrogen fixation. Cyanobacteria have developed a great variety of biochemical, structural, and biotic adaptations ensuring optimal growth and proliferation in diverse oxic environments to counter this difficult situation. Structurally, cyanobacteria reveal remarkable diversity, including the formation of highly differentiated, O2-deplete cells (heterocysts), multicellularity as trichomes, and aggregates, that, among N2-fixing genera, facilitate division of labor between aerobic and anaerobic processes. Cyanobacteria enjoy unique consortial and symbiotic associations with other microorganisms, higher plants, and animals, in which O2 consumption is closely coupled in time and space to its production. Because as prokaryotes they are devoid of O2-consuming organelles (e.g., mitochondria), cyanobacteria have developed alternative strategies for locally protecting O2-sensitive processes, including consortial relationships with other microorganisms. Specific organic compounds released by cyanobacteria are capable of chemotactically attracting bacterial consorts, which in turn attach to the host cyanobacteria, consume O2, and recycle inorganic nutrients within the cyanobacterial "phycosphere." Multicellularity and aggregation lead to localized O2 gradients and hypoxic/anoxic microzones in which O2-sensitive processes can coexist. Microscale partitioning of O2-producing and O2-inhibited processes promotes contiguous and effective metabolite and nutrient exchange between these processes in oxygenated waters, representing a bulk of the world's oceanic and freshwater ecosystems.