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Indigenous microbial enhanced oil recovery (IMEOR) is a promising alternative way to promote oil recovery. It activates oil recovery microorganisms in the reservoir by adding nutrients to the injected water, utilizing microbial growth and metabolism to enhance recovery. However, few studies have focused on the impact of injected nutrients on reservoir microbial community composition and potential functions. This limits the further strategic development of IMEOR. In this study, we investigated the effects of nutrition on the composition of the reservoir bacterial community and functions in the Qizhong block of Xinjiang Oilfield, China, by constructing a long core microbial flooding simulation device. The results showed that the microbial community structure of the reservoir changed from aerobic state to anaerobic state after nutrient injection. Reducing the nutrient concentration increased the diversity and network stability of the reservoir bacterial community. At the same time, the nitrogen metabolism function also showed the same change response. Overall, these results indicated that nutrition significantly affected the community structure and function of reservoir microorganisms. Injecting low concentrations of nutrients may be more beneficial to improve oil recovery. This study is of great significance for guiding IMEOR technology and saving costs at the field site.

Objective To summarize the clinical manifestations and histopathological characteristics of skeletal muscle in scleromyositis patients with positive anti‑Ku or anti‑PM‑Scl antibodies. Methods and Results Retrospective collection of clinical data from 70 scleromyositis patients diagnosed at Peking University First Hospital from January 2010 to March 2023, analysis showed the average onset age of patients was 36.00 (20.75, 51.25) years old. The initial symptoms of 77.14% (54/70) patients was mainly in the proximal limbs myasthenia [74.29% (52/70)], mild to moderate [77.14% (54/70)], and 52.86% (37/70) patients had systemic symptoms such as fatigue or skin involvement during the course of the disease. The serum creatine kinase (CK) level was 2775.00 (995.50, 4995.75) U/L. About 32.86% (23/70) were positive for anti‑Ku antibody, 65.71% (46/70) were positive for anti‑PM‑Scl antibody, 1.43% (1/70) were both positive, and 27.14% (19/70) could also had increased level of other myositis antibodies. The main histopathological changes were inflammatory [41.43% (29/70)] or necrotic [24.29% (17/70)] myopathic pathological changes, presenting as muscle fiber atrophy [91.43% (64/70)], necrosis [68.57% (48/70)] or regeneration [85.71% (60/70)]. Comparison of symptoms, signs and histopathological characteristics of skeletal muscle between patients with positive anti‑Ku antibody and with positive anti‑PM ‑Scl antibody, female proportion (χ2 = 4.381, P = 0.036) and C5b9 deposition damage (χ2 = 4.725, P = 0.030) were higher in the former than those in the latter. Conclusions Scleromyositis patients with positive anti‑Ku or anti‑PM‑Scl antibodies mostly started in young and middle age, mainly manifesting as mild to moderate myasthenia in the proximal limbs, and skeletal muscle inflammatory or necrotic myopathic lesions as characteristic pathological changes. Compared with positive anti ‑ PM ‑ Scl antibody patients, positive anti ‑ Ku antibody scleromyositis patients were mainly female, and skeletal muscle complement deposition was more notable.

Objective To evaluate the diagnostic value of skeletal muscle biopsy in asymptomatic and pauci‑symptomatic hyperCKemia. Methods and Results A total of 146 patients with asymptomatic or pauci ‑ symptomatic hyperCKemia diagnosed in Peking University First Hospital from July 2020 to February 2023 were selected, and skeletal muscle biopsy was performed. About 72.60% (106/146) had histological changes, including muscular dystrophy (n = 73), inflammatory or necrotizing myopathy (n = 16), other myopathy (n = 15), and neurogenic skeletal muscle damage (n = 2). The positive rate of pathological diagnosis was 50.68% (74/146), including muscular dystrophy 82.43% (61/74), inflammatory myopathy 8.11% (6/74) and metabolic myopathy 9.46% (7/74). The positive rate of etiological diagnosis was 85.62% (125/146), including muscular dystrophy 67.20% (84/125), inflammatory myopathy 13.60% (17/125), metabolic myopathy 7.20% (9/125) and other causes 12% (15/125). Compared with different subgroups, the proportion of pathological changes (χ2 = 14.043, P = 0.000; χ2 = 12.740, P = 0.000), the positive rate of pathological diagnosis (χ2 = 10.641, P = 0.001; χ2 = 25.530, P = 0.000) and etiological diagnosis (Fisher's exact probability: P = 0.001; χ2 = 10.811, P = 0.001) in the significantly elevated creatine kinase (CK) level group and the adolescent group was significantly higher than those in the mildly elevated CK level group and the adult group. The positive rate of pathological diagnosis in the asymptomatic group was higher than the pauci‑symptomatic group (χ2 = 4.792, P = 0.029). There were significant differences in the etiological ratio between the mildly elevated CK level group and the significantly elevated CK level group (Fisher's exact probability: P = 0.000), the adolescent group and the adult group (χ2 = 86.149, P = 0.000), and the asymptomatic group and the pauci ‑ symptomatic group (χ2 = 20.608, P = 0.000). Conclusions Skeletal muscle biopsy was important in etiological diagnosis of asymptomatic and pauci‑symptomatic hyperCKemia. Muscular dystrophy is a common cause of asymptomatic and pauci‑symptomatic hyperCKemia.

Objective To report the clinical and pathological features of 4 patients with oculopharyngodistal myopathy type 1 (OPDM1) caused by CGG repeat expansion in the 5'untranslated region (5'UTR) of LRP12 gene. Methods and Results This study included 4 patients with OPDM1 who were admitted to Peking University First Hospital from January 2008 to August 2023. All 4 patients presented with weakness of eyes closed, dysarthria, dysphagia, facial muscle weakness and muscle weakness mainly involving distal muscles. None of 4 patients had restricted eye movements. Two of the patients had ptosis (Case 1 and Case 2). Serum creatine kinase (CK) levels were mildly to moderately elevated (190- 1211 U/L) in 4 patients. Three patients (Case 1, Case 2 and Case 3) underwent lower extremity muscle MRI which showed varying degrees of fatty infiltration, with the soleus and tibialis anterior muscles being worst affected. Skeletal muscle biopsies in all 4 patients showed rimmed vacuoles with muscular dystrophy‑like pathological changes. Immunofluorescence staining revealed p62 ‑ positive and ubiquitin ‑ positive intranuclear inclusions in all 4 patients. Genetic testing revealed that all 4 patients carried CGG repeat expansion in the 5'UTR of the LRP12 gene. Conclusions Most OPDM1 patients start with weakness in the distal extremities of both limbs and dysarthria. The involvement of muscles in the lower extremities is asymmetrical, and the involvement of tissues and organs other than muscles is not obvious. The remaining clinical phenotype and pathological features are consistent with other subtypes of OPDM.

Objective To retrospectively analyze the clinical sign and symptom, pathological and genetic characteristics of a case of hereditary myopathy with early respiratory failure (HMERF). Methods and Results A 26‑year‑old female patient presented with muscle weakness (including the proximal and distal arms and lower legs) and myalgia, typical daytime and nighttime respiratory failure symptoms. The serum creatine kinase (CK, 258 U/L) and creatine kinase isoenzyme (CK ‑ MB, 17.80 ng/ml) levels were increased. The EMG showed myogenic changes, and thigh muscle MRI showed selective semitendinous muscle involvement. The skeletal muscle biopsy showed the formation of cytoplasm arranged in the submuscular membrane like a "necklace". Gene test revealed a mutation of TTN gene with c.90211T > C (p. Cys30071Arg). The final diagnosis was HMERF. Conclusions The possibility of HMERF should be considered in patients with unexplained respiratory failure, especially with muscle weakness. Skeletal muscle biopsy and genetic test can make a definitive diagnosis.

BackgroundNuclear isomers are crucial in cosmic element synthesis and have potential applications in controlling nuclear energy release. Specifically, Europium (Eu) is significant in fundamental studies. For instance, 152Eu is used as a reference source for radioactive experiments, and its isomeric state 152m1Eu has a probability of 73% to produce cosmological p-nuclei 152Gd with β- decay. Therefore, 152m1Eu is a crucial nuclide in the nuclearsynthesis of p-nuclei 152Gd.PurposeThis study aims to realize the efficient excitation of 152m1Eu with a bremsstrahlung source generated by laser plasma.MethodsFirstly, the laser-plasma bremsstrahlung source was utilized to achieve the efficient excitation of 152m1Eu (45.6 keV, T1/2=9.31 h) in the experiment with yields of 8×104 particles/shot by this isotope. Then, numerical simulations of the yield of 152m1, m2Eu were performed using the Geant4-GENBOD program to get generation time, and peak excitation efficiency evolution with electron temperature.ResultsThe results demonstrate that when the electron temperature reaches 15 MeV, the yield of 152m1, m2Eu approaches saturation. When the incident electron charge is 17.6 nC, the yield of 152m1Eu is approximately 8×106 particles/shot, and that of 152m2Eu is approximately 2×105 particles/shot. The generation time of 152m1, m2Eu in the target is approximately 32 ps. When the electron temperature reaches 15 MeV, the peak excitation efficiency of 152m1Eu is expected to be ~1017 particles/s, and that of 152m2Eu is expected to be ~1016 particles/s.ConclusionsThe ultrashort ultrahigh intensity laser technology can significantly enhance the excitation efficiency of isotopes of the same nucleus, and this will provide an important research avenue for the study of cosmic element synthesis and nuclear energy release control applications.

Microbial Enhanced Oil Recovery (MEOR) is an option for recovering oil from depleted reservoirs. Numerous field trials of MEOR have confirmed distinct microbial community structure in diverse production wells within the same block. The variance in the reservoir microbial communities, however, remains ambiguously documented. In this study, an 8 m long core microbial flooding simulation device was built on a laboratory scale to study the dynamic changes of the indigenous microbial community structure in the Qizhong Block, Xinjiang oil field. During the MEOR, there was an approximate 34% upswing in oil extraction. Based on the 16S rRNA gene high-throughput sequencing, our results indicated that nutrition was one of the factors affecting the microbial communities in oil reservoirs. After the introduction of nutrients, hydrocarbon oxidizing bacteria became active, followed by the sequential activation of facultative anaerobes and anaerobic fermenting bacteria. This was consistent with the hypothesized succession of a microbial ecological “food chain” in the reservoir, which preliminarily supported the two-step activation theory for reservoir microbes transitioning from aerobic to anaerobic states. Furthermore, metagenomic results indicated that reservoir microorganisms had potential functions of hydrocarbon degradation, gas production and surfactant production. Understanding reservoir microbial communities and improving oil recovery are both aided by this work.

Objective To report the characteristics of cardiac involvement in a group of patients with mitochondrial encephalomyopathy with lactic academia and stroke⁃like episodes (MELAS). Methods A total of 113 patients with MELAS who were admitted to Peking University First Hospital from January 2010 to December 2019 were included. The type and severity of heart disease were judged by electrocardiogram (ECG) and echocardiography. Cardiac dysfunction and systolic function were assessed by New York Heart Association (NYHA) classification and left ventricular ejection fraction (LVEF). Results All 113 patients were from 112 families, and the main genotype was m. 3243 A＞G (81.42%, 92/113). ECG was performed in 113 cases, among which 14 (12.38%) had abnormal cardiac conduction, including 10 (8.85%) with pre⁃excitation syndrome, 3 (2.65%) with complete or incomplete right bundle branch block, and one (0.88%) with Ⅰ° atrioventricular block. Echocardiography was performed in 70 cases, among which 18 (25.71%) had myocardial lesions, including 13 (18.57%) with myocardial damage and 5 (7.14%) with pulmonary hypertension (PH). Only one case had NYHA Ⅱ with decreased left ventricular systolic function. In 32 patients with cardiac disease, only one patient presented cardiac symptoms in the 7th year of the course of disease. Conclusions MELAS patients may have various manifestations of cardiac involvement, including cardiomyopathy, heart failure, arrhythmia, and so on. Attention should be paid to cardiac⁃related examinations.

Karst ecosystems are widely distributed around the world, accounting for 15–20% of the global land area. However, knowledge on microbial ecology of these systems does not match with their global importance. To close this knowledge gap, we sampled three niches including weathered rock, sediment, and drip water inside the Heshang Cave and three types of soils overlying the cave (forest soil, farmland soil, and pristine karst soil). All these samples were subjected to high-throughput sequencing of V4-V5 region of 16S rRNA gene and analyzed with multivariate statistical analysis. Overall, archaeal communities were dominated by Thaumarchaeota, whereas Actinobacteria dominated bacterial communities. Thermoplasmata, Nitrosopumilaceae, Aenigmarchaeales, Crossiella, Acidothermus, and Solirubrobacter were the important predictor groups inside the Heshang Cave, which were correlated to NH4+ availability. In contrast, Candidatus Nitrososphaera, Candidatus Nitrocosmicus, Thaumarchaeota Group 1.1c, and Pseudonocardiaceae were the predictors outside the cave, whose distribution was correlated with pH, Ca2+, and NO2−. Tighter network structures were found in archaeal communities than those of bacteria, whereas the topological properties of bacterial networks were more similar to those of total prokaryotic networks. Both chemolithoautotrophic archaea (Candidatus Methanoperedens and Nitrosopumilaceae) and bacteria (subgroup 7 of Acidobacteria and Rokubacteriales) were the dominant keystone taxa within the co-occurrence networks, potentially playing fundamental roles in obtaining energy under oligotrophic conditions and thus maintaining the stability of the cave ecosystem. To be noted, all the keystone taxa of karst ecosystems were related to nitrogen cycling, which needs further investigation, particularly the role of archaea. The predicted ecological functions in karst soils mainly related to carbohydrate metabolism, biotin metabolism, and synthesis of fatty acid. Our results offer new insights into archaeal ecology, their potential functions, and archaeal interactions with bacteria, which enhance our understanding about the microbial dark matter in the subsurface karst ecosystems.

Salt tolerance is one of the most important problems in the field of environmental governance and restoration. Among the various sources of factors, except temperature, salinity is a key factor that interrupts bacterial growth significantly. In this regard, constant efforts are made for the development of salt-tolerant strains, but few strains with salt tolerance, such as Terribacillus saccharophilus, were found, and there are still few relevant reports about their salt tolerance from complete genomic analysis. Furthermore, with the development of the economy, environmental pollution caused by oil exploitation has attracted much attention, so it is crucial to find the bacteria from T. saccharophilus which could degrade petroleum hydrocarbon even under high-salt conditions. Herein, one T. saccharophilus strain named ZY-1 with salt tolerance was isolated by increasing the salinity on LB medium step by step with reservoir water as the bacterial source. Its complete genome was sequenced, which was the first report of the complete genome for T. saccharophilus species with petroleum hydrocarbon degradation and emulsifying properties. In addition, its genome sequences were compared with the other five strains that are from the same genus level. The results indicated that there really exist some differences among them. In addition, some characteristics were studied. The salt-tolerant strain ZY-1 developed in this study and its emulsification and degradation performance of petroleum hydrocarbons were studied, which is expected to widely broaden the research scope of petroleum hydrocarbon-degrading bacteria in the oil field environment even in the extreme environment. The experiments verified that ZY-1 could significantly grow not only in the salt field but also in the oil field environment. It also demonstrated that the developed salt-tolerant strain can be applied in the petroleum hydrocarbon pollution field for bioremediation. In addition, we expect that the identified variants which occurred specifically in the high-salt strain will enhance the molecular biological understanding and be broadly applied to the biological engineering field.

Objective To summarize the clinical phenotypes and genetic mutations of DNAJB6 related myopathies. Methods We retrospectively reviewed the clinical information, laboratory tests, muscle MRIs, electromyography results, muscle pathology examinations and genetic mutations of 2 patients of DNAJB6 related myopathies from one family and reviewed related published literatures of DNAJB6 related myopathies. Results The proband presented with muscle weakness of both proximal and distal limbs, with lower limbs more serious than upper limbs, and proximal more serious than distal. The father of proband presented with abnormal gait, and he could only climb stairs with assistance. Serum creatine kinase (CK) levels of both patients were normal. Muscle MRIs of both patients showed different degrees of fatty infiltration. Muscle biopsies of both patients showed similar changes with dystrophic features, and some muscle fibers with rimmed vacuoles inside, as well as increased internal nuclei and a few regenerating fibers. Genetic tests proved both patients carried the same DNAJB6 gene variant, c.161A ＞ C (p.Glu54Ala), which was the first report in mainland China. The proband was diagnosed as limb ⁃ girdle muscular dystrophy D1 (LGMD⁃D1) type, and the father of proband was diagnosed as distal myopathy. This family was considered as autosomal dominant DNAJB6 related myopathy. Referring to literature, heterogeneities exist in DNAJB6 related myopathies, and different clinical phenotypes could be presented in one single family. Conclusions The phenotypes of DNAJB6 related myopathies include limb ⁃ girdle muscular dystrophy and distal myopathy. Muscle pathology shows similar changes of rimmed vacuoles and dystrophic features. This reported family further expands the spectrum of phenotypes of DNAJB6 related myopathies. doi：10.3969/j.issn.1672⁃6731.2021.03.013

The wear resistance of TC4 titanium alloy was improved by plasma nitriding and the optimum nitriding temperature was investigated. TC4 titanium alloy was nitrided at 650, 700, 750, 800, 850℃ and 900℃ with LDM1-100 plasma nitriding equipment respectively,the temperature holding time is 10 h for each nitriding treatment. The microstructure, surface morphology, surface roughness, phase structure and hardness of nitrided samples at different temperatures were characterized by optical microscope, scanning electron microscope, white light three-dimensional topography instrument and microhardness tester. The tribological properties of TC4 titanium alloy after plasma nitriding were tested by CETR UMT-3 multifunctional friction and wear tester. The results show that the surface microhardness and roughness of TC4 titanium alloy increase with the increase of temperature. After nitriding at 900℃, the surface microhardness of TC4 titanium alloy reaches 1318HV0.05, which is about 4 times as high as that of the substrate (360HV0.05). The increase of hardness is due to the formation of hard nitride phases (TiN and Ti2N phases) on the surface of nitrided sample and the nitride content increases with the increase of nitriding temperature. The load-carrying capacity of nitrided samples at 800℃ and 900℃ is significantly higher than that of nitriding samples at low temperatures (below 750℃). Compared with the original TC4 sample, the wear volume of the nitrided sample significantly reduces. When nitriding temperature is 850℃, the wear volume of the nitrided sample is 1.2% (1 N), 3.0% (3 N) and 62.2% (5 N) of that of the untreated sample, and the improvement of wear resistance of the sample is the most obvious.

ABSTRACT The geological role of microorganisms has been widely studied in the karst cave ecosystem. However, microbial interactions and ecological functions in such a dark, humid, and oligotrophic habitat have received far less attention, which is crucial to understanding cave biogeochemistry. Herein, microorganisms from weathered rock and sediment along the Heshang Cave depth were analyzed by random matrix theory-based network and Tax4Fun functional prediction. The results showed that although the cave microbial communities have spatial heterogeneity, differential habitats drove the community structure and diversity. Actinobacteria were predominant in weathered rock, whereas Proteobacteria dominated the sediment. The sediment communities presented significantly higher alpha diversities due to the relatively abundant nutrition from the outside by the intermittent stream. Consistently, microbial interactions in sediment were more complex, as visualized by more nodes and links. The abundant taxa presented more positive correlations with other community members in both of the two networks, indicating that they relied on promotion effects to adapt to the extreme environment. The keystones in weathered rock were mainly involved in the biodegradation of organic compounds, whereas the keystone Nitrospira in sediment contributed to carbon/nitrogen fixation. Collectively, these findings suggest that microbial interactions may lead to distinct taxonomic and functional communities in weathered rock and sediment in the subsurface Heshang Cave. IMPORTANCE In general, the constant physicochemical conditions and limited nutrient sources over long periods in the subsurface support a stable ecosystem in karst cave. Previous studies on cave microbial ecology were mostly focused on community composition, diversity, and the relationship with local environmental factors. There are still many unknowns about the microbial interactions and functions in such a dark environment with little human interference. Two representative habitats, including weathered rock and sediment in Heshang Cave, were selected to give an integrated insight into microbial interactions and potential functions. The cooccurrence network, especially the subnetwork, was used to characterize the cave microbial interactions in detail. We demonstrated that abundant taxa primarily relied on promotion effects rather than inhibition effects to survive in Heshang Cave. Keystone species may play important metabolic roles in sustaining ecological functions. Our study provides improved understanding of microbial interaction patterns and community ecological functions in the karst cave ecosystem.

The wear resistance of TC4 titanium alloy was improved by plasma nitriding and the optimum nitriding temperature was investigated. TC4 titanium alloy was nitrided at 650, 700, 750, 800, 850℃ and 900℃ with LDM1-100 plasma nitriding equipment respectively,the temperature holding time is 10 h for each nitriding treatment. The microstructure, surface morphology, surface roughness, phase structure and hardness of nitrided samples at different temperatures were characterized by optical microscope, scanning electron microscope, white light three-dimensional topography instrument and microhardness tester. The tribological properties of TC4 titanium alloy after plasma nitriding were tested by CETR UMT-3 multifunctional friction and wear tester. The results show that the surface microhardness and roughness of TC4 titanium alloy increase with the increase of temperature. After nitriding at 900℃, the surface microhardness of TC4 titanium alloy reaches 1318HV0.05, which is about 4 times as high as that of the substrate (360HV0.05). The increase of hardness is due to the formation of hard nitride phases (TiN and Ti2N phases) on the surface of nitrided sample and the nitride content increases with the increase of nitriding temperature. The load-carrying capacity of nitrided samples at 800℃ and 900℃ is significantly higher than that of nitriding samples at low temperatures (below 750℃). Compared with the original TC4 sample, the wear volume of the nitrided sample significantly reduces. When nitriding temperature is 850℃, the wear volume of the nitrided sample is 1.2% (1 N), 3.0% (3 N) and 62.2% (5 N) of that of the untreated sample, and the improvement of wear resistance of the sample is the most obvious.

Deciphering of the mycobiome in pristine karst caves has been impeded by constraints of remote locations, inaccessibility to specimens and technical limitations, which greatly restricted in-depth understanding of mycobiomes in subterranean ecosystem. Here, mycobiomes of Heshang Cave in south-western karst region of China were investigated by Illumina HiSeq sequencing of fungal rRNA-ITS1 gene across different habitats. In total 793,502 ITS1 reads and 2,179 OTUs from 778 Mb reads after stringent quality control (Q30) and 453 genera, 72 orders and 19 classes within 6 phyla were detected. Ascomycota (42% OTUs) dominated across the five habitats. Shannon-Wiener index varied from 1.25 to 7.62 and community richness was highest in drip waters, followed by weathered rocks, bat guanos, sediments, and air samples. Mycobiomes displayed specificity to five habitats and more distinct OTUs were found in weathered rocks (12%) and drip waters (9%). In contrast, only 6.60% core OTUs were shared by five habitats. Notably, weathered rocks possessed more indicator groups and were revealed for the first time to be dominated by Sordariomycetes (43%). The community richness of air mycobiomes increased from cave entrance to the innermost part and dominated by the indicator groups of Penicillium mallochii (>30%) and P. herquei (>9%). Our work represents the largest attempt to date to a systematical investigation of oligotrophic solution-cave-associated mycobiomes in China. Our discovery of high diversity of mycobiomes in Heshang Cave also suggests that eukaryotic microorganisms may play a crucial role in subsurface environments.

Considering space environmental requirements, a multidisciplinary optimization of a 2 degrees-of-freedom micro linear actuator is carried out to improve the overall performance of a nested flying vehicle in this article. To achieve high-quality microgravity environment, a nested flying vehicle is designed that can be operated inside the Space Station. The electromagnetic actuators are utilized to control the position and posture of the experiment device while the exterior structure is following the movement of the inner system. Each actuator is designed to generate vertical and horizontal forces at the same time. The actuator is composed of two permanent magnets, a 2 degrees-of-freedom coil on a printed circuit board and a steel back yoke. Due to the complexity of structure parameters modification, the geometry, the structural model, electromagnetism model, and multidisciplinary analysis process are integrated based on ModelCenter framework. In this case, the structural model is established using ANSYS/APDL. The electromagnetic analysis is performed by the magnetics postprocessing. The OPTLIB Gradient Optimizer, non-dominated sorting genetic algorithm II, and Design Explorer for multidisciplinary optimization with constraints are utilized for validation mutually. In view of the optimization results, compared with the prototype design based on experience, the width of the back yoke, the weight of actuator, and the residual force have been reduced by 23%, 50%, and 62% while the output forces resulted in an acceptable range.

Enhanced monsoon duration and soil acidification from acid rain, are expected to impact the distribution of microbial communities of surface and subsurface environments, although these impacts are poorly understood for most systems. In central China, soluble carbonate bedrock forms extensive karst landscapes. Current predictions are that the amount of monsoonal precipitation and acid rainfall in central China will increase, which is expected to lead to changes in the pH balance of karst ecosystems. To evaluate the role of pH, TOC and other geochemical parameters (e.g., Ca2+, Mg2+, NH4+, NOx, SO42-) in shaping bacterial communities within a single karst system in central China, samples were collected from the thin surface soils overlying Heshang cave, cave sediments, and weathered cave passage rocks from the entrance, twilight, and dark zones, as well as from epikarstic drip waters inside the cave. Illumina sequencing of 16S rRNA genes and multivariate statistical analyses revealed that each tested community was distinct and the community variability was significantly correlated with pH, total organic carbon, and potassium concentrations. Specifically, surface soils were dominated by Acidobacteria, Verrucomicrobia and Planctomycetes, and diversity significantly decreased with acidic pH values. Nitrospirae, Gemmatimonadetes, Firmicutes, and Chloroflexi were unique to cave sediments, while Actinobacteria and Proteobacteria dominated weathered rocks and drip waters, respectively. The results reveal important implications regarding the effects of acidification on bacterial communities in karst areas, and on the control of pH in shaping bacterial communities throughout a karst system. Increased water flux into and through karst habitats due to monsoonal precipitation may result in deeper penetration of acidic solutions into karst and shift the bacterial communities inside the cave in the future.