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1. Dynamic aqueous transformations of lithium cobalt oxide nanoparticle induce distinct oxidative stress responses of B. subtilis

   https://doi.org/10.1039/D0EN01151G  

   Gari, Metti K.; Lemke, Paul; Lu, Kelly H.; Laudadio, Elizabeth D.; Henke, Austin H.; Green, Curtis M.; Pho, Thomas; Hoang, Khoi Nguyen; Murphy, Catherine J.; Hamers, Robert J.; et al (January 2021, Environmental Science: Nano)

   null (Ed.)

   Lithium cobalt oxide (LiCoO 2 ), an example of nanoscale transition metal oxide and a widely commercialized cathode material in lithium ion batteries, has been shown to induce oxidative stress and generate intracellular reactive oxygen species (ROS) in model organisms. In this study, we aimed to understand the time-dependent roles of abiotic ROS generation and Co ions released in aqueous medium by LiCoO 2 NPs, and examined the induced biological responses in model bacterium, B. subtilis upon exposure. We found that the redox-active LiCoO 2 NPs produced abiotic ROS primarily through H 2 O 2 generation when freshly suspended. Subsequently, the freshly-suspended LiCoO 2 NPs induced additional DNA breakage, and changes in expression of oxidative stress genes in B. subtilis that could not be accounted for by the released Co ions alone. Notably, in 48 hour old LiCoO 2 suspensions, H 2 O 2 generation subsided while higher concentrations of Co ions were released. The biological responses in DNA damage and gene expression to the aged LiCoO 2 NPs recapitulated those induced by the released Co ions. Our results demonstrated oxidative stress mechanisms for bacteria exposed to LiCoO 2 NPs were mediated by the generation of distinct biotic and abiotic ROS species, which depended on the aqueous transformation state of the NPs. This study revealed the interdependent and dynamic nature of NP transformation and their biological consequences where the state of NPs resulted in distinct NP-specific mechanisms of oxidative injury. Our work highlights the need to capture the dynamic transformation of NPs that may activate the multiple routes of oxidative stress responses in cells. 

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2. Mfd deficiency decreases the abundance of complete transcripts of sporulation genes and alters sporogenesis and the structure of dormant Bacillus subtilis spores

   https://doi.org/10.3389/fmicb.2025.1680580  

   Martin, Holly Anne; Heron, Robert; Leyva-Sanchez, Hilda; Perez, Ryan King; Callaway, Amber; Ermi, Tatiana; Picard, Aude; Grifaldo, Jessica; Barnes, Jesse L; Pedraza-Reyes, Mario; et al (October 2025, Frontiers in Microbiology)

   Sporulation is a survival mechanism employed by Firmicutes, includingBacillus subtilis, when facing stressful conditions of growth (e.g., starvation). In this bacterium, the transcription repair coupling factor, Mfd, has been shown to play pivotal roles in sporulation transcription-coupled DNA repair and stress-associated mutagenesis. Recent studies have also revealed an unexpected role of Mfd in regulating gene expression duringB. subtilissporulation. This study examines the effects ofB. subtilisMfd deficiency on the expression of sporulation genes, sporulation efficiency, and spore morphology. In the absence of exogenous DNA damage, we found that Mfd deficiency does not compromise spore germination outgrowth; however, the loss of this factor promoted spore morphological defects and decreased sporulation efficiency. Also, our results confirmed an anomalous pattern of expression of sporulation genes in cells lacking Mfd. These results showed that Mfd influences bacterial physiology beyond DNA repair of actively transcribed genes. 

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3. Does Cellular Metabolism from Primary Fibroblasts and Oxidative Stress in Blood Differ between Mammals and Birds? The (Lack-thereof) Scaling of Oxidative Stress

   https://doi.org/10.1093/icb/icz017  

   Jimenez, A G; O’Connor, E S; Tobin, K J; Anderson, K N; Winward, J D; Fleming, A; Winner, C; Chinchilli, E; Maya, A; Carlson, K; et al (April 2019, Integrative and Comparative Biology)

   Abstract As part of mitonuclear communication, retrograde and anterograde signaling helps maintain homeostasis under basal conditions. Basal conditions, however, vary across phylogeny. At the cell-level, some mitonuclear retrograde responses can be quantified by measuring the constitutive components of oxidative stress, the balance between reactive oxygen species (ROS) and antioxidants. ROS are metabolic by-products produced by the mitochondria that can damage macromolecules by structurally altering proteins and inducing mutations in DNA, among other processes. To combat accumulating damage, organisms have evolved endogenous antioxidants and can consume exogenous antioxidants to sequester ROS before they cause cellular damage. ROS are also considered to be regulated through a retrograde signaling cascade from the mitochondria to the nucleus. These cellular pathways may have implications at the whole-animal level as well. For example, birds have higher basal metabolic rates, higher blood glucose concentration, and longer lifespans than similar sized mammals, however, the literature is divergent on whether oxidative stress is higher in birds compared with mammals. Herein, we collected literature values for whole-animal metabolism of birds and mammals. Then, we collected cellular metabolic rate data from primary fibroblast cells isolated from birds and mammals and we collected blood from a phylogenetically diverse group of birds and mammals housed at zoos and measured several parameters of oxidative stress. Additionally, we reviewed the literature on basal-level oxidative stress parameters between mammals and birds. We found that mass-specific metabolic rates were higher in birds compared with mammals. Our laboratory results suggest that cellular basal metabolism, total antioxidant capacity, circulating lipid damage, and catalase activity were significantly lower in birds compared with mammals. We found no body-size correlation on cellular metabolism or oxidative stress. We also found that most oxidative stress parameters significantly correlate with increasing age in mammals, but not in birds; and that correlations with reported maximum lifespans show different results compared with correlations with known aged birds. Our literature review revealed that basal levels of oxidative stress measurements for birds were rare, which made it difficult to draw conclusions. 

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4. Active pH regulation facilitates Bacillus subtilis biofilm development in a minimally buffered environment

   https://doi.org/10.1128/mbio.03387-23  

   Tran, Peter; Lander, Stephen M; Prindle, Arthur (March 2024, mBio)

   Kline, Kimberly A (Ed.)

   ABSTRACT Biofilms provide individual bacteria with many advantages, yet dense cellular proliferation can also create intrinsic metabolic challenges including excessive acidification. Because such pH stress can be masked in buffered laboratory media—such as MSgg commonly used to studyBacillus subtilisbiofilms—it is not always clear how such biofilms cope with minimally buffered natural environments. Here, we report howB. subtilisbiofilms overcome this intrinsic metabolic challenge through an active pH regulation mechanism. Specifically, we find that these biofilms can modulate their extracellular pH to the preferred neutrophile range, even when starting from acidic and alkaline initial conditions, while planktonic cells cannot. We associate this behavior with dynamic interplay between acetate and acetoin biosynthesis and show that this mechanism is required to buffer against biofilm acidification. Furthermore, we find that buffering-deficient biofilms exhibit dysregulated biofilm development when grown in minimally buffered conditions. Our findings reveal an active pH regulation mechanism inB. subtilisbiofilms that could lead to new targets to control unwanted biofilm growth.IMPORTANCEpH is known to influence microbial growth and community dynamics in multiple bacterial species and environmental contexts. Furthermore, in many bacterial species, rapid cellular proliferation demands the use of overflow metabolism, which can often result in excessive acidification. However, in the case of bacterial communities known as biofilms, these acidification challenges can be masked when buffered laboratory media are employed to stabilize the pH environment for optimal growth. Our study reveals thatB. subtilisbiofilms use an active pH regulation mechanism to mitigate both growth-associated acidification and external pH challenges. This discovery provides new opportunities for understanding microbial communities and could lead to new methods for controlling biofilm growth outside of buffered laboratory conditions. 

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5. Corticosterone and Mitochondrial Efficiency Are Associated With Changes in DNA Oxidative Damage During an Acute Stress Response in Leach's Storm‐Petrels ( Hydrobates leucorhous )

   https://doi.org/10.1002/jez.2917  

   Lichtner, Kayla E; Dziubek, Jack K; Joseph, Nicole A; Chapman, Sarah E; Chace, Tori J; Sun, Dongxiao; Bitzer, Zachary T; Stier, Antoine; Mauck, Robert A; Jones, Patricia L; et al (March 2025, Journal of Experimental Zoology Part A: Ecological and Integrative Physiology)

   ABSTRACT The ability of organisms to effectively respond to challenges is critical for survival. We investigated how an acute stressor affected corticosterone, mitochondrial function, and DNA oxidative damage in a wild population of Leach's storm‐petrels (Hydrobates leucorhous). We conducted a standardized 20‐min handling procedure on storm‐petrel chicks and collected baseline and post‐handling blood samples. We measured plasma corticosterone and red blood cell DNA oxidative damage levels through the detection of a mutated DNA base 8‐Hydroxy‐2'‐deoxyguanosine (8‐OHdG). In addition, we quantified six measures of mitochondrial aerobic metabolism from red blood cells. Overall, the handling stressor increased plasma corticosterone levels and decreased mitochondrial efficiency to produce ATP. Although the increase in corticosterone was inversely related to the change in DNA oxidative damage, the decrease in mitochondrial efficiency was positively correlated with the change in DNA oxidative damage. Thus, over an acute stress response, individuals who had the largest increase in corticosterone also had the least amount of oxidative damage. In addition, individuals who prioritized ATP production during the acute stress also showed higher levels of oxidative damage. This work highlights the complex pathways by which corticosterone and mitochondrial efficiency affect oxidative damage during acute stress, providing new insights into the trade‐offs underlying physiological responses in wild animals. 

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