Search for: All records

ABSTRACT Posttranscriptional modifications to tRNA are critical elements for the folding and functionality of these adaptor molecules. Sulfur modifications in tRNA are installed by specialized enzymes that act on cognate tRNA substrates at specific locations. Most studied organisms contain a general cysteine desulfurase to mobilize sulfur for the synthesis of S-tRNA and other thio-cofactors. Bacillus subtilis and other Gram-positive bacteria encode multiple cysteine desulfurases that partner with specific sulfur acceptors in the biosynthesis of thio-cofactors. This metabolic layout suggests an alternate mode of regulation in these biosynthetic pathways. In this study, tRNA modifications were exploited as a readout for the functionality of pathways involving cysteine desulfurases. These analyses showed that the relative abundance of 2-thiouridine-modified tRNA (s 2 U) responds to sulfur availability in the growth medium in a dose-dependent manner. This study found that low sulfur concentrations lead to decreased levels of the s 2 U cysteine desulfurase YrvO and thiouridylase MnmA, without altering the levels of other cysteine desulfurases, SufS, NifS, and NifZ. Analysis of pathway metabolites that depend on the activity of cysteine desulfurases indicates that sulfur nutrient availability specifically impacts s 2 U accumulation while having no effect on the levels of other S-modified tRNA or activity levels of Fe-S enzymes. Collectively, these results support a model in which s 2 U tRNA serves as a marker for sulfur availability in B. subtilis . IMPORTANCE The 2-thiouridine (s 2 U) tRNA modification is found ubiquitously across all domains of life. YrvO and MnmA, the enzymes involved in this modification, are essential in B. subtilis , confirming the well-established role of s 2 U in maintaining translational efficiency and, consequently, cellular viability. Herein, we show that in the model Gram-positive organism Bacillus subtilis , the levels of s 2 U are responsive to sulfur availability. Downregulation of the s 2 U biosynthetic components leads to lower s 2 U levels, which may serve as a signal for the slowing of the translational apparatus during cellular nutrient insufficiency. Our findings provide the basis for the identification of a potential bacterial mode of regulation during S-metabolite depletion that may use s 2 U as a marker of suboptimal metabolic status. 

Currently threatening the world of medicine is a growing number of antibiotic-resistant diseases. More specifically, bacteria and nematodes have gained resistance to many of the world’s leading antibiotics and nematicides, respectively, making infections more difficult to treat. Subsequently, these parasitic organisms are able to continue damaging crops and other living organisms like humans without strong interference. To help people and the environment, the development of new and novel antibiotics is vital. Previous research suggests that phytochemicals are a potential solution that will not only help inhibit bacterial growth but also reduce nematode survival. We hypothesized that Myrica cerifera, a plant often used by the Lumbee tribe to treat illness, possesses antibacterial and nematicidal properties. To answer our hypothesis, we began by collecting plant specimens to extract material for biological assays and to subsequently isolate and elucidate the structures of active components. The extract was evaluated for antibacterial properties with an agar diffusion assay and then nematicidal properties using Caenorhabditis elegans. M. cerifera extract was added onto an agar lawn at various doses, and the nematodes’ lifespans were scored. The findings of this study show that extracts of this plant, more commonly referred to as ‘wax myrtle’, do significantly decrease the lifespan of C. elegans and increase the zone of inhibition for Staphylococcus epidermidis and Staphylococcus aureus. In addition, two compounds were isolated and characterized through chemical extraction, chromatographic separation, and spectroscopic analysis. These compounds could potentially be used to treat bacterial and nematode infections.KEYWORDS: Antibacterial; Antimicrobial; Caenorhabditis elegans; Plant extract; Myrica cerifera; Nematicidal; NMR; Phytochemical 

Transfer RNAs (tRNAs) are essential adaptors that mediate translation of the genetic code. These molecules undergo a variety of post-transcriptional modifications, which expand their chemical reactivity while influencing their structure, stability, and functionality. Chemical modifications to tRNA ensure translational competency and promote cellular viability. Hence, the placement and prevalence of tRNA modifications affects the efficiency of aminoacyl tRNA synthetase (aaRS) reactions, interactions with the ribosome, and transient pairing with messenger RNA (mRNA). The synthesis and abundance of tRNA modifications respond directly and indirectly to a range of environmental and nutritional factors involved in the maintenance of metabolic homeostasis. The dynamic landscape of the tRNA epitranscriptome suggests a role for tRNA modifications as markers of cellular status and regulators of translational capacity. This review discusses the non-canonical roles that tRNA modifications play in central metabolic processes and how their levels are modulated in response to a range of cellular demands. 

Online learning has gained increased popularity in recent years. However, with online learning, teacher observation and intervention is lost, creating a need for technologically observable characteristics that can compensate for this limitation. The present study used a wide array of sensing mechanisms including eye tracking, galvanic skin response (GSR) recording, facial expression analysis, and summary note-taking to monitor participants while they watched and recalled an online video lecture. We explored the link between these human-elicited responses and learning outcomes as measured by quiz questions. Results revealed GSR to be the best indicator of the challenge level of the lecture material. Yet, eye tracking and GSR remain difficult to capture when monitoring online learning as the requirement to remain still impacts natural behavior and leads to more stoic and unexpressive faces. Continued work on methods ensuring naturalistic capture are critical for broadening the use of sensor technology in online learning, as are ways to fuse these data with other input, such as structured and unstructured data from peer-to-peer or student-teacher interactions.