Seasonal dynamics of the microbial community in a strong-flavor baijiu fermentation.

BACKGROUND: The microbial community plays a crucial role in Chinese strong-flavor baijiu (SFB) fermentation. However, the seasonal dynamics of the microbial community in the SFB fermentation system and its contribution to the unique flavor of SFB have not been fully elucidated. In this study, we investigated the seasonal dynamics of the microbial community through 16S rRNA and ITS gene sequencing. RESULTS: The results revealed significant temporal dynamics of microbial communities and environmental variables throughout the four seasons. The influence of seasons on fungal communities was found to be more significant than on bacterial communities. The diversity of bacteria was higher during the winter and summer, whereas fungal diversity was more prominent in summer and autumn. Stochastic processes maintained their dominance in microbial assembly throughout all four seasons but the significance of heterogeneous selection increased during summer for both bacteria and fungi, whereas homogeneous selection became more pronounced during winter for fungi. The pH and environmental temperature were important drivers of microbial community assembly across different seasons, primarily impacting the core genera responsible for the production of major volatile flavor compounds (VFCs), especially ethyl caproate. CONCLUSION: These findings provide new insights into the impact of seasons on microbial communities and hold promise for improving the quality-control measures for SFB brewed in different seasons. © 2024 Society of Chemical Industry.

Interconnected versus unconnected microorganisms: Does it matter in anaerobic digestion functioning.

Microorganisms in anaerobic digestion (AD) are essential for wastes/pollutants treatment and energy recovery. Due to microbial enormous diversity, developing effective perspectives to understand microbial roles therein is urgent. This study conducted AD of swine manure, used an ensemble-based network analysis to distinguish interconnected, unconnected, copresence (positively interconnected) and mutual-exclusion (negatively interconnected) microorganisms within microbial communities, and explored their importance towards AD performances, using amplicon sequencing of 16S rRNA and 16S rRNA gene. Our analyses revealed greater importance of interconnected than unconnected microorganisms towards CH4 production and AD multifunctionality, which was attributed to higher niche breadth, deterministic community assembly, community stability and phylogenetic conservatism. The diversity was higher in unconnected than interconnected microorganisms, but was not linked to AD performances. Compared to copresence microorganisms, mutual-exclusion microorganisms showed greater and equal importance towards CH4 production and AD multifunctionality, which was attributed to their roles in stabilizing microbial communities. The increased feedstock biodegradability, by replacing part of manure with fructose or apple waste, hardly affected the relative importance of interconnected versus unconnected microorganisms towards CH4 production or AD multifunctionality. Our findings develop a new framework to understand microbial roles, and have important implications in targeted manipulation of critical microorganisms in waste-treatment systems.

Microbial phylogenetic relatedness links to distinct successional patterns of bacterial and fungal communities.

The mechanisms underlying microbial community dynamics and co-occurrence patterns along ecological succession are crucial for understanding ecosystem recovery but remain largely unexplored. Here, we investigated community dynamics and taxa co-occurrence patterns in bacterial and fungal communities across a well-established chronosequence of post-mining lands spanning 54 years of recovery. Bacterial community structures became increasingly phylogenetically clustered with soil age at early successional stages and varied less at later successional stages. The dynamics of bacterial community phylogenetic structures were determined by the changes in the soil vegetation cover along succession. The dynamics of fungal community phylogenetic structures did not significantly correlate with soil age, soil properties or vegetation cover, and were mainly attributed to stochastic processes. Along succession, the common decrease in the bacterial co-occurrence complexity and in the average pairwise phylogenetic distances between co-occurring bacteria implied a decrease in potential bacterial cooperation. The increased complexity of fungal co-occurrence along succession was independent of phylogenetic relatedness between co-occurring fungi. This study provides new sights into ecological mechanisms underlying bacterial and fungal community succession.

Size-segregated physicochemical properties of inhalable particulate matter in a tunnel-ventilated layer house in China.

This study investigated the physicochemical properties of the particles in a typical commercial laying hen barn in Southeast China. Mass concentrations and size distributions of the particulate matter (PM) and the key components (incl. organic carbon (OC), element carbon (EC), and the water-soluble inorganic ions (WSIIs)) were analyzed. The result shows that the mass concentrations of PM accumulated along with the airflow inside the house, with the total mass of the sampling particles increasing from 843.66 ± 160.74 µg/m3 at the center of the house to 1264.93 ± 285.70 µg/m3 at the place close to exhaust fans. The particles with the aerodynamic equivalent diameter, Dp > 9 µm, coarse particles (2.1 µm < Dp ≤ 9 µm), fine particles (Dp ≤ 2.1 µm) accounted for around 50%, 40%, and 10% of the total mass of the sampling particles, respectively. Mass closure analysis shows secondary inorganic ions (NH4+, SO42- and NO3-) were abundant in the fine-mode fraction and OC accounted for more than 40% of the coarse particles. Size distribution analysis shows that the three secondary inorganic ions were bimodally distributed, and the rest tested components were unimodally distributed. The ratios of OC/EC in fine particles were smaller than those in the coarse particles. The equivalent concentration of WSIIs indicated that fine particles were slightly acidic, and the large size particles were slightly alkaline. Knowledge gained from this study will lead to a better understanding of physicochemical properties, sources, and formation of PM.

The stroke mechanism, clinical presentation, and radiological feature of bilateral medial medullary infarction.

BACKGROUND: Bilateral medial medullary infarction (BMMI) is a rare type of posterior circulation stroke. The aim of this study is to characterize its stroke mechanisms, clinical manifestations, neuroradiological features, and prognosis. METHODS: From January 2015 to June 2021, a retrospective review of 15 patients diagnosed with BMMI was conducted. The clinical and neuroradiological features were summarized by our experienced neurologists. RESULTS: Fifteen patients (12 male, 3 female), ranging in age from 48 to 72 years, satisfied the inclusion criteria. The common clinical presentations included motor weakness (100%), deep sensory disturbance (93.3%), vertigo/dizziness (80%), dysarthria (93.3%), and dysphagia (66.7%). Vertically, infarct lesions in the rostral medulla were observed in all included patients. Horizontally, "heart appearance," "Y appearance," and "fan appearance" infarcts occurred in 9 cases (60%), 5 cases (33.3%), and 1 (6.7%) case, respectively. Patients (53.3%) had severe stenosis or occlusion in unilateral vertebral artery (VA), and 33.3% had normal findings in the vertebrobasilar artery. Patients (93.3%) achieved poor prognosis. CONCLUSION: BMMI is more frequently located in the rostral medulla and comprises three forms of infarction. The two main stroke etiologies of BMMI are large-artery atherosclerosis (LAA) and small vessel disease (SVD). BMMI is always associated with bad clinical outcome.

Transcriptional response of Pseudomonas chenduensis strain MBR to cadmium toxicity.

Cadmium (Cd) contamination has resulted in serious environmental pollution and threatens human health and ecosystems. Our recent studies have demonstrated that Pseudomonas chenduensis strain MBR can decrease Cd bio-availability and reduce Cd accumulation in rice; however, the transcriptional mechanisms underlying the bacterial response during and particularly after Cd bioremediation are still unclear. In this study, we used RNA-Seq to investigate the transcriptional profiles of strain MBR during and after Cd bioremediation. During Cd bioremediation, MBR removed all Cd2+ ions in solution within 24 h, accompanied by 564 upregulated and 363 downregulated expressed genes compared with that of the control (without Cd supplementation). Specifically, under Cd stress, the upregulation of czc (czcA, czcB, and czcC) and mer (merA, merT, merC, and merP) genes enabled Cd efflux from the cytoplasm and conferred resistance of MBR to Cd toxicity. The upregulation of genes (algK, algX, and alg44) related to biofilm formation enabled Cd absorption and contributed to Cd bioremediation. After Cd bioremediation, MBR was transferred to non-Cd medium, and the genes related to histidine metabolism and flagellar assembly still showed similar expression patterns as those during bioremediation (defined as Cd legacy effects). However, the genes involved in Cd resistance and bioremediation were not influenced by Cd legacy effects. This study provides new and thorough insights into the molecular mechanisms underlying Cd bioremediation by a functional microbe. KEY POINTS: • The upregulation of czc and mer genes is responsible for MBR resistance to Cd. • The upregulation of genes related to biofilm formation contributes to Cd bioremediation. • Cd effects on genes involved in histidine metabolism and flagellar assembly are long-lasting.

Molecular mechanism of nanoparticulate TiO2 induction of axonal development inhibition in rat primary cultured hippocampal neurons.

Numerous studies have demonstrated the in vitro and in vivo neurotoxicity of nanoparticulate titanium dioxide (nano-TiO2 ), a mass-produced material for a large number of commercial and industrial applications. The mechanism of nano-TiO2 -induced inhibition of axonal development, however, is still unclear. In our study, primary cultured hippocampal neurons of 24-hour-old fetal Sprague-Dawley rats were exposed to 5, 15, or 30 µg/mL nano-TiO2 for 6, 12, and 24 hours, and the toxic effects of nano-TiO2 exposure on the axons development were detected and its molecular mechanism investigated. Nano-TiO2 accumulated in hippocampal neurons and inhibited the development of axons as nano-TiO2 concentrations increased. Increasing time in culture resulted in decreasing axon length by 32.5%, 36.6%, and 53.8% at 6 hours, by 49.4%, 53.8%, and 69.5% at 12 hours, and by 44.5%, 58.2%, and 63.6% at 24 hours, for 5, 15, and 30 µg/mL nano-TiO2 , respectively. Furthermore, nano-TiO2 downregulated expression of Netrin-1, growth-associated protein-43, and Neuropilin-1, and promoted an increase of semaphorin type 3A and Nogo-A. These studies suggest that nano-TiO2 inhibited axonal development in rat primary cultured hippocampal neurons and this phenomenon is related to changes in the expression of axon growth-related factors.

Dynamics and potential roles of abundant and rare subcommunities in the bioremediation of cadmium-contaminated paddy soil by Pseudomonas chenduensis.

Microbial bioremediation of heavy metal-contaminated soil is a potential technique to reduce heavy metals in crop plants. However, the dynamics and roles of the local microbiota in bioremediation of heavy metal-contaminated soil following microbial application are rarely reported. In this study, we used Pseudomonas chenduensis strain MBR for bioremediation of Cd-contaminated paddy soil and investigated its effects on the dynamics of the local soil bacterial community and Cd accumulation in rice. Cd accumulation in rice grains and roots were significantly reduced by the addition of the strain MBR. The addition of the strain MBR caused greater changes in bacterial communities in rhizosphere soil than in bulk soil. MBR enhanced the roles of microbial communities in transformation of Cd fractions, especially in rhizosphere soil. The strain MBR likely regulated abundant subcommunities more than rare subcommunities to improve Cd bioremediation, especially in rhizosphere soil. Consequently, the dynamics and functional roles of the local microbial communities differed significantly during bioremediation between abundant and rare subcommunities and between rhizosphere soil and bulk soil. This study provides new insight into the microbiota-related mechanisms underlying bioremediation.

Protective immunity induced by Eimeria common antigen 14-3-3 against Eimeria tenella, Eimeria acervulina and Eimeria maxima.

BACKGROUND: Avian coccidiosis is often caused by co-infection with several species of Eimeria worldwide. Developing a multivalent vaccine with an antigen common to multiple Eimeria species is a promising strategy for controlling clinical common co-infection of Eimeria. In the previous study, 14-3-3 was identified as one of the immunogenic common antigen in E. tenella, E. acervulina and E. maxima. The aim of the present study was to evaluate the immunogenicity and protective efficacy of Ea14-3-3 in the form of DNA vaccine against infection with three species of Eimeria both individually and simultaneously. RESULTS: After vaccination with pVAX-Ea14-3-3, the Ea14-3-3 gene was transcribed and expressed in the injected muscles. Vaccination with pVAX-Ea14-3-3 significantly increased the proportion of CD4+ and CD8+ T lymphocytes and produced a strong IgY response in immunized chickens. Similarly, pVAX-Ea14-3-3 stimulated the chicken's splenocytes to produce high levels of Th1-type (IFN-γ, IL-2) and Th2-type (IL-4) cytokines. The vaccine-induced immune response was responsible to increase weight gain, decreased the oocyst output, and alleviated enteric lesions significantly in immunized chickens as compared to control group, in addition to induce moderate anti-coccidial index (ACI). CONCLUSION: These results indicate that Ea14-3-3 is highly immunogenic and capable to induce significant immune responses. Furthermore, Ea14-3-3 antigen can provide effective protection against infection with Eimeria tenella, Eimeria acervulina, Eimeria maxima both individually and in combination with three Eimeria species. Significant outcomes of our study provide an effective candidate antigen for developing a multivalent Eimeria vaccine against mixed infection with various Eimeria species under natural conditions.

Rice Plasma Membrane Proteomics Reveals Magnaporthe oryzae Promotes Susceptibility by Sequential Activation of Host Hormone Signaling Pathways.

Plant plasma membrane (PM) plays important roles in immune response. Here, we utilized quantitative mass spectrometry to explore rice PM protein composition and dynamic changes during Magnaporthe oryzae infection. We report, thus far, the largest rice PM proteome dataset with 3,906 identified proteins, among which 484 proteins were differentially expressed after M. oryzae infection. One third of the identified proteins are predicted to have at least one transmembrane domain. Half of the identified proteins are predicted to have binding functions and over one third of the proteins have enzyme-related functions. In addition, Gene Ontology analyses revealed that abscisic acid (ABA) and cytokinin (CK) signaling were sequentially activated after M. oryzae infection in rice. We found that the activation of ABA signaling and the suppression of rice immune response occurred at the early infection stage, while the activation of CK signaling, the upregulation of sugar transporter genes expression, and the nutrient efflux of infected rice cells occurred at later infection stage. Thus, we further propose that M. oryzae activates ABA signaling to repress rice immune signaling for initial invasion and redirects nutrient efflux of infected cells for massive growth at the later infection stage.

Major ionic compositions of fine particulate matter in an animal feeding operation facility and its vicinity.

Animal feeding operations (AFOs) produce particulate matter (PM) and gaseous pollutants. Investigation of the chemical composition of PM2.5 inside and in the local vicinity of AFOs can help to understand the impact of the AFO emissions on ambient secondary PM formation. This study was conducted on a commercial egg production farm in North Carolina. Samples of PM2.5 were collected from five stations, with one located in an egg production house and the otherfour located in the vicinity ofthe farm alongfour wind directions. The major ions of NH4+, Na+, K+, SO4(2-), Cl-, and NO3- were analyzed using ion chromatography (IC). In the house, the mostly abundant ions were SO4(2-), Cl-, and K+. At ambient stations, SO4(2-), and NH4+ were the two most abundant ions. In the house, NH4+, SO4(2-), and NO3- accounted for only 10% of the PM2.5 mass; at ambient locations, NH4+, SO4(2-), and NO3- accounted for 36-41% of the PM2.5 mass. In the house, NH4+ had small seasonal variations indicating that gas- phase NH3. was not the only major force driving its gas-particle partitioning. At the ambient stations, NH4+ had the highest concentrations in summer In the house, K+, Na+, and Cl- were highly correlated with each other In ambient locations, SO4(2-) and NH4+ had a strong correlation, whereas in the house, SO4(2-) and NH4+ had a very weak correlation. Ambient temperature and solar radiation were positively correlated with NH4+ and SO4(2-). This study suggests that secondary PM formation inside the animal house was not an important source of PM2.5. In the vicinity, NH3 emissions had greater impact on PM2.5 formation.

Comprehensive analysis reveals that LTBR is a immune-related biomarker for glioma.

Glioma is a common malignant brain tumor with great heterogeneity and huge difference in clinical outcomes. Although lymphotoxin (LT) beta receptor (LTBR) has been linked to immune system and response development for decades, the expression and function in glioma have not been investigated. To confirm the expression profile of LTBR, integrated RNA-seq data from glioma and normal brain tissues were analyzed. Functional enrichment analysis, TMEscore analysis, immune infiltration, the correlation of LTBR with immune checkpoints and ferroptosis, and scRNAseq data analysis in gliomas were in turn performed, which pointed out that LTBR was pertinent to immune functions of macrophages in gliomas. In addition, after being trained and validated in the tissue samples of the integrated dataset, an LTBR DNA methylation-based prediction model succeeded to distinguish gliomas from non-gliomas, as well as the grades of glioma. Moreover, by virtue of the candidate LTBR CpG sites, a prognostic risk-score model was finally constructed to guide the chemotherapy, radiotherapy, and immunotherapy for glioma patients. Taken together, LTBR is closely correlated with immune functions in gliomas, and LTBR DNA methylation could serve as a biomarker for diagnosis and prognosis of gliomas.

Field Implementation of Precision Livestock Farming: Selected Proceedings from the 2nd U.S. Precision Livestock Farming Conference.

Precision Livestock Farming (PLF) involves the real-time monitoring of images, sounds, and other biological, physiological, and environmental parameters to assess and improve animal health and welfare within intensive and extensive production systems [...].

Public and professional education on urgent therapy for acute ischemic stroke: a community-based intervention in Changsha.

Excessive delay of presentation for stroke in China is reported. In this study, an intervention trial was conducted to promote urgent therapy for acute ischemic stroke. Two communities in Changsha were selected as either intervention or control community from November 2007 to December 2011. Public and professional education was regularly implemented in the intervention community. Publics' knowledge about early identification and urgent therapy of ischemic stroke was surveyed before and after intervention in the two communities. During the intervention period, first-ever ischemic stroke cases occurring in the intervention community (intervention group) and that in the control community (control group) were collected and followed for 90 days. After intervention, the publics' knowledge levels in the intervention community improved significantly. Intervention group' average presentation time was shorter than control group (8.3 ± 5.8 vs. 10.5 ± 6.5 h, P = 0.018). Percentage of presentation time within 3 h (48.0 %), the rate of ambulance use (59.0 %), and thrombolytic therapy (9.3 %) in the intervention group was all obviously higher than that in the control group (21.5, 41.3, and 4.5, respectively). When admitted, the intervention group had lower mean systolic blood pressure (160.8 ± 26.7 vs. 164.7 ± 26.8 mmHg, P = 0.000) than control group. Survivors in the intervention group were more likely to be in higher Barthel index scoring groups than that in the control group at day 90 [(75, 50-100) vs. (65, 35-90), P = 0.035]. Public and professional education may promote prompt presentation and urgent therapy for ischemic stroke, which may be helpful for patients' prognosis.

Identification of Bioaerosols Released from an Egg Production Facility in the Southeast United States.

This field study investigated biological characteristics of aerosols emitted from a commercial egg production farm (layer operation). Bioaerosol samples were taken on this farm at five sampling locations covering emission source (inside a layer barn) and four ambient surrounding stations at four wind directions. All-glass impingers (AGI) were used for the field sampling. AGI fluid samples were plated in duplicate on Trypticase Soy Agar for growth of bacteria and Sabouraud Dextrose Agar for growth of fungi. The most prominent bacterial colony types were identified using a combination of methods that include recording characteristics of colony morphology; performing a Gram staining method and metabolic analyses using the Biolog system. Results from thirty-five AGI samples taken at the five stations through seven sampling events over four seasons indicate that there were significantly lower total bacterial concentrations in the samples collected from ambient stations as compared with the samples collected in the layer house; the mean bacterial concentration at the in-house sampling station was 3.86×10(5)±1.74×10(5) cfu/m(3), whereas the mean bacterial concentrations at four ambient stations in the vicinity of the farm ranged from 1.3×10(3) to 6.2×10(3) cfu/m(3) with no significant differences in mean among ambient stations. There were also no significant differences in fungi concentrations among all sampling stations. Mean fungi concentrations at the in-house station was 3.0×10(3)±4.45×10(3) cfu/m(3), whereas the mean concentrations at the ambient stations ranged from 7.4×10(3) to 1.7×10(4) cfu/m(3). The most prominent bacterial species differed among all five stations. Three of the most prominent bacteria from samples taken at all five stations were gram positive. Fungal type also differed from station to station.

Severe hypernatremia during postoperative care in patients with craniopharyngioma.

Purpose: We aimed to describe and predict the risk of severe hypernatremia after surgical resection of craniopharyngioma and to identify the association of water intake, urine output, and sodium level change in the patients. Method: The outcome was postoperative severe hypernatremia. We identified risk factors associated with hypernatremia using multivariable regression. We trained machine learning models to predict the outcome. We compared serum sodium change, intravenous input, oral input, total input, urine output, and net fluid balance according to different nurse shifts. Results: Among 234 included patients, 125 developed severe hypernatremia after surgery. The peak incidence occurred during day 0 and day 6 after surgery. The risk was increased in patients with gross total resection (odds ratio (OR) 2.41, P < 0.001), high Puget classification (OR 4.44, P = 0.026), preoperative adrenal insufficiency (OR 2.01, P = 0.040), and preoperative hypernatremia (OR 5.55, P < 0.001). The random forest algorithm had the highest area under the receiver operating characteristic curve (0.770, 95% CI, 0.727-0.813) in predicting the outcome and was validated in the prospective validation cohort. Overnight shifts were associated with the highest serum sodium increase (P = 0.010), less intravenous input (P < 0.001), and less desmopressin use (P < 0.001). Conclusion: The overall incidence of severe hypernatremia after surgical resection of craniopharyngioma was significant, especially in patients with gross total resection, hypothalamus distortion, preoperative adrenal insufficiency, and preoperative severe hypernatremia. Less intravenous input and less desmopressin use were associated with serum sodium increases, especially during overnight shifts.

Functional conservation of microbial communities determines composition predictability in anaerobic digestion.

A major challenge in managing and engineering microbial communities is determining whether and how microbial community responses to environmental alterations can be predicted and explained, especially in microorganism-driven systems. We addressed this challenge by monitoring microbial community responses to the periodic addition of the same feedstock throughout anaerobic digestion, a typical microorganism-driven system where microorganisms degrade and transform the feedstock. The immediate and delayed response consortia were assemblages of microorganisms whose abundances significantly increased on the first or third day after feedstock addition. The immediate response consortia were more predictable than the delayed response consortia and showed a reproducible and predictable order-level composition across multiple feedstock additions. These results stood in both present (16 S rRNA gene) and potentially active (16 S rRNA) microbial communities and in different feedstocks with different biodegradability and were validated by simulation modeling. Despite substantial species variability, the immediate response consortia aligned well with the reproducible CH4 production, which was attributed to the conservation of expressed functions by the response consortia throughout anaerobic digestion, based on metatranscriptomic data analyses. The high species variability might be attributed to intraspecific competition and contribute to biodiversity maintenance and functional redundancy. Our results demonstrate reproducible and predictable microbial community responses and their importance in stabilizing system functions.

More persistent weather causes a pronounced soil microbial legacy but does not impact subsequent plant communities.

A soil history of exposure to extreme weather may impact future plant growth and microbial community assembly. Currently, little is known about whether and how previous precipitation regime (PR)-induced changes in soil microbial communities influence plant and soil microbial community responses to a subsequent PR. We exposed grassland mesocosms to either an ambient PR (1 day wet-dry alternation) or a persistent PR (30 days consecutive wet-dry alternation) for one year. This conditioned soil was then inoculated as a 10 % fraction into 90 % sterilized "native" soil, after which new plant communities were established and subjected to either the ambient or persistent PR for 60 days. We assessed whether past persistent weather-induced changes in soil microbial community composition affect soil microbial and plant community responses to subsequent weather persistence. The historical regimes caused enduring effects on fungal communities and only temporary effects on bacterial communities, but did not trigger soil microbial legacy effects on plant productivity when exposed to either current PR. This study provides experimental evidence for soil legacy of climate persistence on grassland ecosystems in response to subsequent climate persistence, helping to understand and predict the influences of future climate change on soil biota.

A coordination complex system for generic, ultrafast, and sensitive multimode fluorescent staining of biomolecules.

Gel electrophoresis staining methodologies documented thus far are largely utilized in a biomolecule context-dependent manner. We report herein the development of a generic, ultrafast, and sensitive multimode fluorescent system for the efficient identification of DNA, RNA, and proteins. Interaction between a positively charged, planar ligand-based coordination complex with partner biomolecule leads to aggregation-induced fluorescence quenching and allows for the image contrast generation within one minute. Alternatively, successive reactions of the biomolecule-loaded gel with cation and ligand, in either order of sequence, provide an equally effective staining efficacy. Image contrast reversal is accomplished through a facile washing or photobleaching procedure. The versatility in the applicable target species and signal generation modes provides a hint at the design of novel staining structures and potentially enables the high-throughput readout of biomolecules.

Field evaluation of particulate matter measurements using tapered element oscillating microbalance in a layer house.

The tapered element oscillating microbalance (TEOM) is one type of continuous ambient particulate matter (PM) monitor. Adsorption and desorption of moisture and semivolatile species may cause positive or negative artifacts in TEOM PM mass measurement. The objective of this field study was to investigate possible uncertainties associated with TEOM measurements in the poultry operation environment. For comparisons of TEOM with filter-based gravimetric method, four instruments (TEOM-PM10, low-volume PM10 sampler TEOM-PM2.5, and PM2.5 speciation sampler) were collocated and tested inside a poultry house for PM2.5 and PM10 (PM with aerodynamic equivalent diameter < or =2.5 and < or =10 microm, respectively) measurements. Fifteen sets of 24-hr PM10 concentrations and 13 sets of 24-hr PM2.5 measurements were obtained. Results indicate that compared with filter-based gravimetric method, TEOM gave significantly lower values of both PM10 and PM2.5 mass concentrations. For PM10, the average ratio of TEOM to the gravimetric method was 0.936. For PM2.5, the average ratio of TEOM to the gravimetric method was 0.738. Particulate matter in the poultry houses possibly contains semivolatile compounds and moisture due to high levels of relative humidity (RH) and gas pollutants. The internal heating mechanism of the TEOM may cause losses in mass through volatilization. To investigate the effects of TEOM settings on concentration measurements, the heaters of two identical TEOMs were set at 50 degrees C, 30 degrees C, or no heating at all. They were collocated and tested for total suspended particle (TSP), PM10, and PM25 measurements in layer house for 6 weeks. For all TSR PM10, and PM2.5 measurements, the internal TEOM temperature setting had a significant effect (P < 0.05). Significantly higher PM mass concentrations were measured at lower temperature settings. The effects of environmental (i.e., temperature, RH, NH3 and CO2 concentrations) and instrumental (i.e., filter loading and noise) parameters on PM measurements were also assessed using regression analysis.