Defects in the flagellar motor increase synthesis of poly-γ-glutamate in Bacillus subtilis.

Bacillus subtilis swims in liquid media and swarms over solid surfaces, and it encodes two sets of flagellar stator homologs. Here, we show that B. subtilis requires only the MotA/MotB stator during swarming motility and that the residues required for stator force generation are highly conserved from the Proteobacteria to the Firmicutes. We further find that mutants that abolish stator function also result in an overproduction of the extracellular polymer poly-γ-glutamate (PGA) to confer a mucoid colony phenotype. PGA overproduction appeared to be the result of an increase in the expression of the pgs operon that encodes genes for PGA synthesis. Transposon mutagenesis was conducted to identify insertions that abolished colony mucoidy and disruptions in known transcriptional regulators of PGA synthesis (Com and Deg two-component systems) as well as mutants defective in transcription-coupled DNA repair (Mfd)-reduced expression of the pgs operon. A final class of insertions disrupted proteins involved in the assembly of the flagellar filament (FliD, FliT, and FlgL), and these mutants did not reduce expression of the pgs operon, suggesting a second mechanism of PGA control.

The cell biology of peritrichous flagella in Bacillus subtilis.

Bacterial flagella are highly conserved molecular machines that have been extensively studied for assembly, function and gene regulation. Less studied is how and why bacteria differ based on the number and arrangement of the flagella they synthesize. Here we explore the cell biology of peritrichous flagella in the model bacterium Bacillus subtilis by fluorescently labelling flagellar basal bodies, hooks and filaments. We find that the average B. subtilis cell assembles approximately 26 flagellar basal bodies and we show that basal body number is controlled by SwrA. Basal bodies are assembled rapidly (< 5 min) but the assembly of flagella capable of supporting motility is rate limited by filament polymerization (> 40 min). We find that basal bodies are not positioned randomly on the cell surface. Rather, basal bodies occupy a grid-like pattern organized symmetrically around the midcell and that flagella are discouraged at the poles. Basal body position is genetically determined by FlhF and FlhG homologues to control spatial patterning differently from what is seen in bacteria with polar flagella. Finally, spatial control of flagella in B. subtilis seems more relevant to the inheritance of flagella and motility of individual cells than the motile behaviour of populations.

Long-Term Temporal Trends of Real-World Healthcare Costs Associated with Nivolumab Plus Ipilimumab and Pembrolizumab Plus Axitinib as First-Line Treatment for Advanced or Metastatic Renal Cell Carcinoma.

INTRODUCTION: Nivolumab plus ipilimumab (NIVO + IPI) and pembrolizumab plus axitinib (PEM + AXI) are first-line (1L) treatments for advanced or metastatic renal cell carcinoma (aRCC), although the long-term trends in their associated real-world healthcare costs are not well defined. We compared the real-world healthcare costs of patients with aRCC who received 1L NIVO + IPI or PEM + AXI over 24 months. METHODS: Adults with RCC and secondary malignancy who initiated 1L NIVO + IPI or PEM + AXI were identified in the Merative MarketScan Commercial and Medicare Supplemental Databases (01/01/2004 to 09/30/2021). All-cause and RCC-related healthcare costs (unadjusted and adjusted) were assessed per patient per month (PPPM) at 6-month intervals post-treatment initiation (index date) up to 24 months, and differences between the NIVO + IPI and PEM + AXI cohorts were compared. RESULTS: Of 325 patients with aRCC, 219 received NIVO + IPI and 106 received PEM + AXI as the 1L treatment. According to patients' follow-up length, the analyses for months 7-12 included 210 patients in the NIVO + IPI cohort and 103 in the PEM + AXI cohort; months 13-18 included 119 and 48 patients, respectively; and months 19-24 included 81 and 25 patients. PPPM unadjusted all-cause total costs were $46,348 for NIVO + IPI and $38,097 for PEM + AXI in months 1-6; $26,840 versus $27,983, respectively, in months 7-12; $22,899 versus $25,137 in months 13-18; and $22,279 versus $27,947 in months 19-24. PPPM unadjusted RCC-related costs were $44,059 for NIVO + IPI and $36,456 for PEM + AXI in months 1-6; $25,144 versus $26,692, respectively, in months 7-12; $21,645 versus $23,709 in months 13-18; and $20,486 versus $25,515 in months 19-24. PPPM costs declined more rapidly for patients receiving NIVO + IPI compared to those receiving PEM + AXI, resulting in significantly lower all-cause costs associated with NIVO + IPI during months 19-24 (difference - $10,914 [95% confidence interval - $21,436, - $1091]) and RCC-related costs during months 7-12 (- $4747 [(- $8929, - $512]) and 19-24 (- $10,261 [- $20,842, - $421]) after adjustment. Cost savings for NIVO + IPI versus PEM + AXI were driven by differences in drug costs which, after adjustment, were significantly lower in months 7-12 (difference - $5555 [all-cause], - $5689 [RCC-related]); 13-18 (- $7217 and - $6870, respectively); and 19-24 (- $16,682 and - $16,125). CONCLUSION: Although the real-world PPPM healthcare costs of 1L NIVO + IPI were higher compared with PEM + AXI in the first 6 months of treatment, the costs associated with NIVO + IPI rapidly declined thereafter, resulting in significantly lower costs vs. PEM + AXI from months 7 to 24.

Treatment Preferences Among Patients with Renal Cell Carcinoma: Results from a Discrete Choice Experiment.

Introduction: The treatment landscape for advanced/metastatic renal cell carcinoma (aRCC) has evolved quickly with the introduction of immunotherapies as a first-line treatment option. This study examined the preferences of patients with aRCC to better understand the characteristics of preferred treatments and the tradeoffs patients are willing to make when choosing treatment. Methods and Materials: An online, cross-sectional survey was conducted in the US from May to August 2022 with adult patients with aRCC. A discrete-choice experiment assessed treatment preferences for aRCC. Attributes were identified through literature review and qualitative interviews and included progression-free survival, survival time, objective response rate, duration of response, risk of serious side effects, quality of life (QoL), and treatment regimen. Results: Survey results from 299 patients with aRCC were analyzed. Patients had a mean age of 55.7 years, were primarily White (50.5%) and were evenly representative of males (49.8%) and females (48.8%). Improvements in all attributes influenced treatment choice. On average, increasing survival time from 10% to 55% was most important, followed by improvements in QoL (ie, from worsens a lot to improves) and improvements to treatment regimen convenience (ie, less frequent infusions). Risk of serious adverse events and increased progression-free time, objective response rate (ORR), and duration of response (DOR) were of lesser importance. Conclusion: In this study, patients highlighted that improving survival time was the most important and that QoL is also an important consideration. Discussions during treatment decision-making may benefit from broader conversations around treatment characteristics, including impacts on QoL and convenience of the regimen.

The EpsE flagellar clutch is bifunctional and synergizes with EPS biosynthesis to promote Bacillus subtilis biofilm formation.

Many bacteria inhibit motility concomitant with the synthesis of an extracellular polysaccharide matrix and the formation of biofilm aggregates. In Bacillus subtilis biofilms, motility is inhibited by EpsE, which acts as a clutch on the flagella rotor to inhibit motility, and which is encoded within the 15 gene eps operon required for EPS production. EpsE shows sequence similarity to the glycosyltransferase family of enzymes, and we demonstrate that the conserved active site motif is required for EPS biosynthesis. We also screen for residues specifically required for either clutch or enzymatic activity and demonstrate that the two functions are genetically separable. Finally, we show that, whereas EPS synthesis activity is dominant for biofilm formation, both functions of EpsE synergize to stabilize cell aggregates and relieve selective pressure to abolish motility by genetic mutation. Thus, the transition from motility to biofilm formation may be governed by a single bifunctional enzyme.

Tracing the domestication of a biofilm-forming bacterium.

Over the course of more than a century of laboratory experimentation, Bacillus subtilis has become "domesticated," losing its ability to carry out many behaviors characteristic of its wild ancestors. One such characteristic is the ability to form architecturally complex communities, referred to as biofilms. Previous work has shown that the laboratory strain 168 forms markedly attenuated biofilms compared with the wild strain NCIB3610 (3610), even after repair of a mutation in sfp (a gene involved in surfactin production) previously known to impair biofilm formation. Here, we show that in addition to the sfp mutation, mutations in epsC, swrA, and degQ are necessary and sufficient to explain the inability of the laboratory strain to produce robust biofilms. Finally, we show that the architecture of the biofilm is markedly influenced by a large plasmid present in 3610 but not 168 and that the effect of the plasmid can be attributed to a gene we designate rapP. When rapP is introduced into 168 together with wild-type alleles of sfp, epsC, swrA, and degQ, the resulting repaired laboratory strain forms biofilms that are as robust as and essentially indistinguishable in architecture from those of the wild strain, 3610. Thus, domestication of B. subtilis involved the accumulation of four mutations and the loss of a plasmid-borne gene.

Role of the sigmaD-dependent autolysins in Bacillus subtilis population heterogeneity.

Exponentially growing populations of Bacillus subtilis contain two morphologically and functionally distinct cell types: motile individuals and nonmotile multicellular chains. Motility differentiation arises because RNA polymerase and the alternative sigma factor sigma(D) activate expression of flagellin in a subpopulation of cells. Here we demonstrate that the peptidoglycan-remodeling autolysins under sigma(D) control, LytC, LytD, and LytF, are expressed in the same subpopulation of cells that complete flagellar synthesis. Morphological heterogeneity is explained by the expression of LytF that is necessary and sufficient for cell separation. Moreover, LytC is required for motility but not at the level of cell separation or flagellum biosynthesis. Rather, LytC appears to be important for flagellar function, and motility was restored to a LytC mutant by mutation of either lonA, encoding the LonA protease, or a gene encoding a previously unannotated swarming motility inhibitor, SmiA. We conclude that heterogeneous activation of sigma(D)-dependent gene expression is sufficient to explain both the morphological heterogeneity and functional heterogeneity present in vegetative B. subtilis populations.

Regulation of flagellar motility during biofilm formation.

Many bacteria swim in liquid or swarm over solid surfaces by synthesizing rotary flagella. The same bacteria that are motile also commonly form nonmotile multicellular aggregates called biofilms. Biofilms are an important part of the lifestyle of pathogenic bacteria, and it is assumed that there is a motility-to-biofilm transition wherein the inhibition of motility promotes biofilm formation. The transition is largely inferred from regulatory mutants that reveal the opposite regulation of the two phenotypes. Here, we review the regulation of motility during biofilm formation in Bacillus, Pseudomonas, Vibrio, and Escherichia, and we conclude that the motility-to-biofilm transition, if necessary, likely involves two steps. In the short term, flagella are functionally regulated to either inhibit rotation or modulate the basal flagellar reversal frequency. Over the long term, flagellar gene transcription is inhibited and in the absence of de novo synthesis, flagella are diluted to extinction through growth. Both short-term and long-term motility inhibition is likely important to stabilize cell aggregates and optimize resource investment. We emphasize the newly discovered flagellar functional regulators and speculate that others await discovery in the context of biofilm formation.