Dentistry from Ancient Phoenicia to Contemporary Lebanon: The USJ Faculty of Dental Medicine in Beirut.

In 2023, the Faculty of Dental Medicine, Saint Joseph University of Beirut (USJ) celebrated its 100th anniversary, marking a century of unwavering commitment to academic excellence. This milestone offers a valuable opportunity to navigate the history and evolution of dentistry in Lebanon, from its ancient roots in Phoenicia to its modern developments. It chronicles the transformative journey of dentistry while recognizing the key role played against all odds by the Society of Jesus and Saint Joseph University of Beirut in fostering the growth of dentistry as a distinct medical discipline.

Sex differences in tobacco use, attempts to quit smoking, and cessation among dual users of cigarettes and e-cigarettes: Longitudinal findings from the US Population Assessment of Tobacco and Health Study.

SIGNIFICANCE: A growing number of adults use more than one tobacco product, with dual use of cigarettes and e-cigarettes being the most common combination. Monitoring sex disparities in tobacco use is a public health priority. However, little is known regarding whether dual users differ by sex. METHODS: Data came from Waves 4-6 (12/2016-11/2021) of the Population Assessment of Tobacco and Health Study, a US nationally-representative longitudinal survey. This analysis included current adult dual users of cigarettes and e-cigarettes. We used weighted generalized estimating equations to assess the association between sex and (1) making a cigarette quit attempt (n = 1882 observations from n = 1526 individuals) and (2) smoking cessation (n = 2081 observations from n = 1688 individuals) across two wave pairs, adjusting for age, education, ethnicity, time-to-first cigarette after waking, and e-cigarette use frequency. RESULTS: Among US dual users, 14.1% (95% Confidence Intervals [Cl] = 11.9-16.4) of females and 23.4% (20.0-26.9) of males were young adults (aged 18-24), 11.7% (9.2-14.2) of females and 14.4% (11.6-17.2) of males had

Sex differences in tobacco use, attempts to quit smoking, and cessation among dual users of cigarettes and e-cigarettes: Longitudinal findings from the US Population Assessment of Tobacco and Health Study.

SIGNIFICANCE: A growing number of adults use more than one tobacco product, with dual use of cigarettes and e-cigarettes being the most common combination. Monitoring sex disparities in tobacco use is a public health priority. However, little is known regarding whether dual users differ by sex. METHODS: Data came from Waves 4-6 (12/2016-11/2021) of the Population Assessment of Tobacco and Health Study, a US nationally-representative longitudinal survey. This analysis included current adult dual users of cigarettes and e-cigarettes. We used weighted generalized estimating equations to assess the association between sex and (1) making a cigarette quit attempt (n = 1882 observations from n = 1526 individuals) and (2) smoking cessation (n = 2081 observations from n = 1688 individuals) across two wave pairs, adjusting for age, education, ethnicity, time-to-first cigarette after waking, and e-cigarette use frequency. RESULTS: Among US dual users, 14.1% (95% Confidence Intervals [Cl] = 11.9-16.4) of females and 23.4% (20.0-26.9) of males were young adults (aged 18-24), 11.7% (9.2-14.2) of females and 14.4% (11.6-17.2) of males had

Exercise in a natural environment increases program compliance in people with chronic migraine: A pilot cross-over randomized trial.

Adverse side effects from pharmacological treatments cause people with migraine to delay or avoid taking medication. Exercise is effective, but the effect of environment is unknown. The purpose was to determine if a natural environment affects monthly migraine load. Sedentary individuals (8 female, 1 non-binary) who experienced migraines participated. Participants completed one month of exercise (3 x week, 30-min, 60-70% estimated HRmax) indoors as well as in a natural outdoor environment in a randomized counterbalanced order. Migraine load was determined using the Headache Impact Test (HIT-6) and Migraine Disability Assessment (MIDAS) at the beginning and end of each month. Data were analyzed using repeated measures ANOVA. No interactions were evident for HIT-6 (p = 0.80), MIDAS (p = 0.72), migraine days (p = 0.508), or pain intensity (p = 0.66). No main effects were noted. Compliance was greater in the outdoor environment, with more exercise sessions completed in nature (Indoor = 72%, Outdoor = 90%, p < 0.001). Exercise environment did not impact MIDAS or HIT-6 questionnaire results, number of migraine days, or pain intensity. While there was no reduction in migraine load, it is possible that other health benefits were experienced due to greater compliance in a natural environment.

Efficacy and safety of dolutegravir/lamivudine in virologically suppressed female participants: week 48 data from the pooled TANGO and SALSA studies.

OBJECTIVES: Women represent >50% of people with HIV globally but have historically been underrepresented in clinical trials. We evaluated the efficacy and safety of switching to dolutegravir/lamivudine (DTG/3TC) vs continuing their current antiretroviral regimen (CAR) by sex assigned at birth (female and male) in virologically suppressed adults with HIV-1 without prior virological failure in a pooled analysis of two randomized controlled trials. METHODS: This analysis included 48-week data from the phase 3 TANGO and SALSA studies. Primary and key secondary endpoints included proportions of participants with HIV-1 RNA ≥50 and <50 copies/mL at week 48, respectively. Safety was also assessed. RESULTS: Of 1234 participants, 250 (DTG/3TC, n = 133; CAR, n = 117) were female at birth. Week 48 proportions of participants with Snapshot HIV-1 RNA ≥50 copies/mL were similar regardless of sex at birth (DTG/3TC vs CAR: female, <1% [1/133] vs 2% [2/117]; male, <1% [1/482] vs <1% [3/502]). Proportions with HIV-1 RNA <50 copies/mL were high across sexes and treatment groups (DTG/3TC vs CAR: female, 91% [121/133] vs 89% [104/117]; male, 94% [455/482] vs 94% [471/502]). Immunological response with DTG/3TC was slightly higher in female participants. Incidences of adverse events leading to withdrawal and serious adverse events were low and comparable between treatment groups and across sexes. Weight gain was higher with DTG/3TC than with CAR among female participants aged ≥50 years (treatment difference 2.08 kg [95% confidence interval 0.40-3.75]). CONCLUSIONS: Results confirm the robustness of DTG/3TC as a switch option in virologically suppressed females with HIV-1, with outcomes similar to those in males.

Electronic nicotine delivery systems (ENDS): Frequency of use and smoking-cessation efforts among U.S. women of reproductive age.

OBJECTIVE: Reducing harm from combustible cigarette use among women of reproductive age (WRA) is critical given their potential vulnerability to multigenerational adverse impacts of cigarette smoking. Although electronic nicotine delivery systems (ENDS) are not approved smoking cessation aids in the US, many WRA who smoke report using ENDS to help quit smoking. Associations between ENDS use patterns and smoking-cessation efforts among US WRA remain unclear. METHODS: Using the Population Assessment of Tobacco and Health (PATH) Study, we examined whether baseline (Wave 3 or 4) ENDS use frequency predicted (a) making a cigarette quit attempt (QA) and (b) successful quitting by follow-up (Wave 4 or 5, respectively) among WRA (N = 2834; 72.1% non-Hispanic White). RESULTS: Daily ENDS use predicted greater adjusted odds of making a QA than non-daily (AOR = 1.63, 95% CI = 1.03, 2.59) and no ENDS use (AOR = 1.97, 95% CI = 1.23, 3.14), and greater odds of successful smoking cessation than non-daily use (AOR = 2.37, 95% CI = 1.31, 4.26). Daily ENDS use did not significantly improve odds of successful smoking cessation compared to no ENDS use (AOR = 1.62, 95% CI = 0.97, 2.69). Non-daily ENDS use did not significantly improve odds of making a QA (AOR = 1.21, 95% CI = 0.94, 1.56) and hindered successful smoking cessation compared to no ENDS use (AOR = 0.68, 95% CI = 0.48, 0.98). CONCLUSIONS: These findings suggest that benefits of ENDS for smoking cessation in WRA may be greatest among those who use ENDS daily. WRA who choose to use ENDS to help quit would be well-informed by evidence that non-daily ENDS use may impede smoking cessation.

Role of genetic analysis of products of conception and PGT in managing early pregnancy loss.

This article considers the addition of comprehensive 24-chromosomal microarray (CMA) analysis of products of conception (POC) to a standard evaluation for recurrent pregnancy loss (RPL) to help direct treatment towards expectant management versus IVF with preimplantation genetic testing for aneuploidies (PGT-A). The review included retrospective data from 65,333 miscarriages, a prospective evaluation of 378 couples with RPL who had CMA testing of POC and the standard workup, and data from an additional 1020 couples who were evaluated for RPL but did not undergo CMA testing of POC. Aneuploidy in POC explained the pregnancy loss in 57.7% (218/378) of cases. In contrast, the full RPL evaluation recommended by the American Society for Reproductive Medicine identified a potential cause in only 42.9% (600/1398). Combining the data from the RPL evaluation and the results of genetic testing of POC provides a probable explanation for the loss in over 90% (347/378) of women. Couples with an unexplained loss after the standard evaluation with POC aneuploidy accounted for 41% of cases; PGT-A may be considered after expectant management. Conversely, PGT-A would have a limited role in those with a euploid loss and a possible explanation after the standard workup. Categorizing a pregnancy loss as an explained versus unexplained loss after the standard evaluation combined with the results of CMA testing of POC may help identify patients who would benefit from expectant management versus PGT-A.

Serotype-Specific Epidemiological Patterns of Inapparent versus Symptomatic Primary Dengue Virus Infections: A 17-year cohort study in Nicaragua.

Dengue is the most prevalent mosquito-borne viral disease and a major public health problem worldwide. Most primary infections with the four dengue virus serotypes (DENV1-4) are inapparent; nonetheless, whether the distribution of symptomatic versus inapparent infections by serotype varies remains unknown. Here, we present (1) the evaluation of a multiplex DENV1-4 envelope domain III multiplex microsphere-based assay (EDIII-MMBA) to serotype inapparent primary infections and (2) its application leveraging 17 years of prospective sample collection from the Nicaraguan Pediatric Dengue Cohort Study (PDCS). First, we evaluated the performance of the EDIII-MMBA with samples characterized by RT-PCR or focus reduction neutralization test. Next, we analyzed 46% (N=574) of total inapparent primary DENV infections in the PDCS with the EDIII-MMBA to evaluate the epidemiology of inapparent infections. Remaining infections were inferred using stochastic imputation, taking year and neighborhood into account. Infection incidence and percentage of inapparent, symptomatic, and severe infections were analyzed by serotype. The EDIII-MMBA demonstrated excellent overall accuracy (100%, 95.8-100%) for serotyping symptomatic and inapparent primary DENV infections when evaluated against gold-standard serotyping methods. We found that a significant majority of primary infections were inapparent, with DENV3 exhibiting the highest likelihood of symptomatic and severe primary infections (Pooled OR compared to DENV1 = 2.13, 95% CI 1.28-3.56, and 6.75, 2.01-22.62, respectively), whereas DENV2 was similar to DENV1 in both analyses. Significant within- and between-year variation in serotype distribution between symptomatic and inapparent infections and circulation of serotypes undetected in symptomatic cases were observed in multiple years. Our study indicates that case surveillance skews the perceived epidemiological footprint of DENV. We reveal a more complex and intricate pattern of serotype distribution in inapparent infections. The significant differences in infection outcomes by serotype emphasizes the need for vaccines with balanced immunogenicity and efficacy across serotypes.

Noncanonical assembly, neddylation and chimeric cullin-RING/RBR ubiquitylation by the 1.8 MDa CUL9 E3 ligase complex.

Ubiquitin ligation is typically executed by hallmark E3 catalytic domains. Two such domains, 'cullin-RING' and 'RBR', are individually found in several hundred human E3 ligases, and collaborate with E2 enzymes to catalyze ubiquitylation. However, the vertebrate-specific CUL9 complex with RBX1 (also called ROC1), of interest due to its tumor suppressive interaction with TP53, uniquely encompasses both cullin-RING and RBR domains. Here, cryo-EM, biochemistry and cellular assays elucidate a 1.8-MDa hexameric human CUL9-RBX1 assembly. Within one dimeric subcomplex, an E2-bound RBR domain is activated by neddylation of its own cullin domain and positioning from the adjacent CUL9-RBX1 in trans. Our data show CUL9 as unique among RBX1-bound cullins in dependence on the metazoan-specific UBE2F neddylation enzyme, while the RBR domain protects it from deneddylation. Substrates are recruited to various upstream domains, while ubiquitylation relies on both CUL9's neddylated cullin and RBR domains achieving self-assembled and chimeric cullin-RING/RBR E3 ligase activity.

Social jet lag impairs exercise volume and attenuates physiological and metabolic adaptations to voluntary exercise training.

Social jet lag (SJL) is a misalignment between sleep and wake times on workdays and free days. SJL leads to chronic circadian rhythm disruption and may affect nearly 70% of the general population, leading to increased risk for cardiometabolic diseases. This study investigated the effects of SJL on metabolic health, exercise performance, and exercise-induced skeletal muscle adaptations in mice. Ten-week-old C57BL/6J mice (n = 40) were allocated to four groups: control sedentary (CON-SED), control exercise (CON-EX), social jet lag sedentary (SJL-SED), and social jet lag exercise (SJL-EX). CON mice were housed under a 12:12-h light-dark cycle. SJL was simulated by implementing a 4-h phase delay for 3 days to simulate "weekends," followed by a 4-h phase advance back to "weekdays," for 6 wk. EX mice had free access to a running wheel. Graded exercise tests (GXTs) and glucose tolerance tests (GTTs) were performed at baseline and after intervention to monitor the effects of exercise and social jet lag on cardiorespiratory and metabolic health, respectively. SJL led to alterations in activity and running patterns and clock gene expression in skeletal muscle and decreased average running distance (P < 0.05). SJL-SED mice gained significantly more weight compared with CON-SED and SJL-EX mice (P < 0.01). SJL impaired fasting blood glucose and glucose tolerance compared with CON mice (P < 0.05), which was partially restored by exercise in SJL-EX mice. SJL also blunted improvements in exercise performance and mitochondrial content in the quadriceps. These data suggest that SJL blunted some cardiometabolic adaptations to exercise and that proper circadian hygiene is necessary for maintaining health and performance.NEW & NOTEWORTHY In mice, disrupting circadian rhythms with social jet lag for 6 wk caused significant weight gain, higher fasting blood glucose, and impaired glucose tolerance compared with control. Voluntary exercise in mice experiencing social jet lag prevented weight gain, though the mice still experienced increased fasting blood glucose and impaired exercise performance compared with trained mice not experiencing social jet lag. Social jet lag seems to be a potent circadian rhythm disruptor that impacts exercise-induced training adaptations.

Effects of Acute Sleep Deprivation on the Physiological Response to Woodsmoke and Exercise.

OBJECTIVE: To evaluate sleep deprivation effects on the acute physiological response to a combined stressor of woodsmoke and exercise. METHODS: Ten participants completed two exercise trials (8 hours of sleep vs 4 hours) with woodsmoke. Trials were conducted in a crossover design. Key measures examined before and after each trial included heart rate variability, pulse wave velocity, blood pressure, pulmonary function testing, and oxidative stress. RESULTS: Acute sleep deprivation experienced before exercise and woodsmoke exposure did not impact metrics of heart rate variability, pulse wave velocity, pulmonary function testing, blood pressure, or oxidative stress. CONCLUSIONS: Acute sleep deprivation did not amplify physiologic metrics in response to moderate-intensity aerobic exercise with inhaled woodsmoke. Although findings do not eliminate the negative impacts of inhaling woodsmoke, more research is needed to understand the acute effects of woodsmoke exposure on the cardiovascular system. 1.

Evaluation of the long-term outcomes of the University of Michigan's Practice-Oriented Research Training (PORT) program.

The University of Michigan created the Practice-Oriented Research Training (PORT) program and implemented it between 2008 and 2018. The PORT program provided research training and funding opportunities for allied healthcare professionals. The program consisted of weekly didactics and group discussion related to topics relevant to developing specific research ideas into projects and funding for a mentored research project for those who submitted a competitive grant application. The goal of this evaluation was to assess the long-term impact of the PORT program on the research careers of the participants. Ninety-two participants (74 staff and 18 faculty) participated in both phases of the program. A mixed-methods approach to evaluation was used; 25 participants who received funding for their research completed surveys, and semi-structured interviews were conducted with eight program participants. In addition, data were collected on participants' publication history. Fifteen out of the 74 staff participants published 31 first-authored papers after participating in PORT. Twelve out of 15 staff participants who published first-authored papers did so for the first time after participating in the PORT program. Results of quantitative and qualitative analyses suggest that the PORT program had positive impacts on both participants and the research community.

m6A-dependent circular RNA formation mediates tau-induced neurotoxicity.

Circular RNAs (circRNAs), covalently closed RNA molecules that form due to back-splicing of RNA transcripts, have recently been implicated in Alzheimer's disease and related tauopathies. circRNAs are regulated by N6-methyladenosine (m6A) RNA methylation, can serve as "sponges" for proteins and RNAs, and can be translated into protein via a cap-independent mechanism. Mechanisms underlying circRNA dysregulation in tauopathies and causal relationships between circRNA and neurodegeneration are currently unknown. In the current study, we aimed to determine whether pathogenic forms of tau drive circRNA dysregulation and whether such dysregulation causally mediates neurodegeneration. We identify circRNAs that are differentially expressed in the brain of a Drosophila model of tauopathy and in induced pluripotent stem cell (iPSC)-derived neurons carrying a tau mutation associated with autosomal dominant tauopathy. We leverage Drosophila to discover that depletion of circular forms of muscleblind (circMbl), a circRNA that is particularly abundant in brains of tau transgenic Drosophila, significantly suppresses tau neurotoxicity, suggesting that tau-induced circMbl elevation is neurotoxic. We detect a general elevation of m6A RNA methylation and circRNA methylation in tau transgenic Drosophila and find that tau-induced m6A methylation is a mechanistic driver of circMbl formation. Interestingly, we find that circRNA and m6A RNA accumulate within nuclear envelope invaginations of tau transgenic Drosophila and in iPSC-derived cerebral organoid models of tauopathy. Taken together, our studies add critical new insight into the mechanisms underlying circRNA dysregulation in tauopathy and identify m6A-modified circRNA as a causal factor contributing to neurodegeneration. These findings add to a growing literature implicating pathogenic forms of tau as drivers of altered RNA metabolism.

The Effects of Long-Term Dienogest Therapy on In Vitro Fertilization Outcomes in Women with Endometriosis: A Systematic Review and Meta-Analysis.

OBJECTIVES: Assessing dienogest's efficacy in endometriosis patients undergoing in vitro fertilization (IVF). DATA SOURCES: Systematic search in databases (PubMed, MEDLINE, Embase, Web of Science, Cochrane CENTRAL, Google Scholar) until 1 October 2022. STUDY SELECTIONS: Randomized trials and observational studies comparing extended dienogest pre-treatment, no pre-treatment, or gonadotropin-releasing hormone (GnRH) agonist pre-treatment in endometriosis-linked IVF. OUTCOME MEASURES: live birth, clinical pregnancy rates, oocytes collected, miscarriage rate, gonadotropin consumption. DATA EXTRACTIONS AND SYNTHESES: Two authors independently assessed eligibility. Dichotomous variables were analyzed via a random-effect model and Mantel-Haenszel method to calculate weighted estimates and 95% confidence intervals (CI). I2 statistic gauged study heterogeneity; GRADE criteria evaluated evidence quality. CONCLUSIONS: Out of 191 publications, five studies with 723 participants were included. Uncertainty persists on whether prolonged dienogest affects live birth (RR 1.42, 95% CI 0.29 to 6.84; 3 studies, n = 289; I2 86%) and clinical pregnancy rates (RR 1.33, 95% CI 0.31 to 5.65; 3 studies, n = 289; I2 86%) compared to conventional IVF. Moreover, uncertainty remains regarding intervention impact on live birth (RR 1.46, 95% CI 0.63 to 3.37; 1 study, n = 34) and clinical pregnancy rates (RR 1.32, 95% CI 0.78 to 2.23; 3 studies, n = 288; I2 0%) versus long-term GnRH agonist therapy before IVF. Given limited data and very low evidence quality, doubts arise about the benefits of long-term dienogest pre-treatment before conventional IVF in endometriosis patients.

Effects of time-restricted exercise on activity rhythms and exercise-induced adaptations in the heart.

Circadian rhythms play a crucial role in the regulation of various physiological processes, including cardiovascular function and metabolism. Exercise provokes numerous beneficial adaptations in heart, including physiological hypertrophy, and serves to shift circadian rhythms. This study investigated the impact of time-restricted exercise training on exercise-induced adaptations in the heart and locomotor activity rhythms. Male mice (n = 45) were allocated to perform voluntary, time-restricted exercise in the early active phase (EAP), late active phase (LAP), or remain sedentary (SED) for 6 weeks. Subsequently, mice were allowed 24-h ad libitum access to the running wheel to assess diurnal rhythms in locomotor activity. Heart weight and cross-sectional area were measured at sacrifice, and cardiac protein and gene expression levels were assessed for markers of mitochondrial abundance and circadian clock gene expression. Mice rapidly adapted to wheel running, with EAP mice exhibiting a significantly greater running distance compared to LAP mice. Time-restricted exercise induced a shift in voluntary wheel activity during the 24-h free access period, with the acrophase in activity being significantly earlier in EAP mice compared to LAP mice. Gene expression analysis revealed a higher expression of Per1 in LAP mice. EAP exercise elicited greater cardiac hypertrophy compared to LAP exercise. These findings suggest that the timing of exercise affects myocardial adaptations, with exercise in the early active phase inducing hypertrophy in the heart. Understanding the time-of-day dependent response to exercise in the heart may have implications for optimizing exercise interventions for cardiovascular health.

Protection against symptomatic dengue infection by neutralizing antibodies varies by infection history and infecting serotype.

Dengue viruses (DENV1-4) are the most prevalent arboviruses in humans and a major public health concern. Understanding immune mechanisms that modulate DENV infection outcome is critical for vaccine development. Neutralizing antibodies (nAbs) are an essential component of the protective immune response, yet their measurement often relies on a single cellular substrate and partially mature virions, which does not capture the full breadth of neutralizing activity and may lead to biased estimations of nAb potency. Here, we analyze 125 samples collected after one or more DENV infections but prior to subsequent symptomatic or inapparent DENV1, DENV2, or DENV3 infections from a long-standing pediatric cohort study in Nicaragua. By assessing nAb responses using Vero cells with or without DC-SIGN and with mature or partially mature virions, we find that nAb potency and the protective NT50 cutoff are greatly influenced by cell substrate and virion maturation state. Additionally, the correlation between nAb titer and protection from disease depends on prior infection history and infecting serotype. Finally, we uncover variations in nAb composition that contribute to protection from symptomatic infection differently after primary and secondary prior infection. These findings have important implications for identifying antibody correlates of protection for vaccines and natural infections.

ULK1 seen at the single-molecule level during autophagy initiation.

Macroautophagy/autophagy research often involves overexpressing proteins to investigate their localization, function and activity. However, this approach can disturb the inherent balance of cellular components, potentially affecting the integrity of the autophagy process. With the advent of genome-editing techniques like CRISPR-Cas9, it is now possible to tag endogenous proteins with fluorescent markers, enabling the study of their behaviors under more physiologically relevant conditions. Nevertheless, conventional microscopy methods have limitations in characterizing the behaviors of proteins expressed at endogenous levels. This challenge can be overcome by single-molecule localization microscopy (SMLM) methods, which provide single-molecule sensitivity and super-resolution imaging capabilities. In our recent study, we used SMLM in combination with genome editing to explore the behavior of endogenous ULK1 during autophagy initiation, yielding unprecedented insights into the autophagy initiation process.Abbreviation: ATG13: autophagy related 13; ATG14: autophagy related 14; ATG16L1: autophagy related 16 like 1; BECN1: beclin 1; ER: endoplasmic reticulum; GABARAPL1: GABA type A receptor associated protein like 1; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MTORC1: mechanistic target of rapamycin kinase complex 1; PALM: photo-activated localization microscopy; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4/VPS15: phosphoinositide-3-kinase regulatory subunit 4; PtdIns3P: phosphatidylinositol-3-phosphate; SMLM: single-molecule localization microscopy; ULK1: unc-51 like autophagy activating kinase 1; WIPI2: WD repeat domain, phosphoinositide interacting 2.

RiPP enzyme heterocomplex structure-guided discovery of a bacterial borosin α-N-methylated peptide natural product.

Amide peptide backbone methylation is a characteristic post-translational modification found in a family of ribosomally synthesized and post-translationally modified peptide natural products (RiPPs) called borosins. Previously, we bioinformatically identified >1500 putative borosin pathways in bacteria; however, none of the pathways were associated with a known secondary metabolite. Through in-depth characterization of a borosin pathway in Shewanella oneidensis MR-1, we have now identified a bacterially derived borosin natural product named Shewanellamide A. Borosin identification was facilitated by the creation and analysis of a series of precursor variants and crystallographic interrogation of variant precursor and methyltransferase complexes. Along with assaying two proteases from S. oneidensis, probable boundaries for proteolytic maturation of the metabolite were projected and confirmed via comparison of S. oneidensis knockout and overexpression strains. All in all, the S. oneidensis natural product was found to be a 16-mer linear peptide featuring two backbone methylations, establishing Shewanellamide A as one of the few borosin metabolites yet identified, and the first from bacteria.