Control-value appraisals and academic emotions: An intensive longitudinal examination of reciprocal effects.

This study examined the reciprocal relation between lesson-specific perceived cognitive appraisals and academic emotions on an intra-individual level. A daily diary study was conducted using a sample of 266 Chinese Han students (Grades 7-8; 56.8% boys; Mage = 13.70, SDage = 0.52) during 10 mathematics lessons in 2022. Standardized questionnaires were also administered to these students before the daily diary study. The results of the dynamic structural equation modeling revealed significant reciprocal relations between cognitive appraisals and academic emotions within early adolescents and highlighted the role of emotions in guiding cognitive appraisals. Additionally, the study identified similarities and differences in the inter-individual relation between appraisals and emotions across self-reported questionnaires and daily diary measures.

Reliability, validity, and measurement invariance of a Chinese handwriting legibility scale among primary students in central China.

Background: Chinese handwriting has a close relationship with spatial cognition, and the legibility dimension is prominent with its spatial-oriented characteristics. However, handwriting evaluation focusing on the detailed spatial aspects of the legibility dimension in the Chinese context is rare. Aims and methods: We aimed to develop a Chinese Handwriting Legibility Scale (CHLS) and examine its reliability, validity, and measurement invariance among Chinese primary students of different grades. A total of 684 students aged 8-12 years were recruited from a mainstream primary school in central China and were asked to copy a Chinese template as legibly as possible within 4 min. The developed CHLS was used to assess these students' legibility performance. Results: The seven-criteria CHLS favored content validity. The inter-rater reliability was good; however, the scoring instructions need to be refined. Principal component analysis (PCA) revealed a one-factor solution explaining 62.336% of the variance of the seven-criteria CHLS, and confirmatory factor analysis (CFA) confirmed its appropriateness. There was a high internal consistency (α = 0.902). In terms of measurement invariance, the factor structures and loadings of the CHLS were consistent across students of different grades; however, significant intercept variations were detected between students of Grades 2 and 4. Conclusion: CHLS may be effective for evaluating Chinese handwriting legibility performance in the Chinese primary school context in the central region. Students' Chinese handwriting legibility performance may have developmental specificity in different grades.

Microbial diversity and metabolic function in duodenum, jejunum and ileum of emu (Dromaius novaehollandiae).

Emus (Dromaius novaehollandiae), a large flightless omnivorous ratite, are farmed for their fat and meat. Emu fat can be rendered into oil for therapeutic and cosmetic use. They are capable of gaining a significant portion of its daily energy requirement from the digestion of plant fibre. Despite of its large body size and low metabolic rate, emus have a relatively simple gastroinstetinal (GI) tract with a short mean digesta retention time. However, little is known about the GI microbial diversity of emus. The objective of this study was to characterize the intraluminal intestinal bacterial community in the different segments of small intestine (duodenum, jejunum, and ileum) using pyrotag sequencing and compare that with the ceca. Gut content samples were collected from each of four adult emus (2 males, 2 females; 5-6 years old) that were free ranged but supplemented with a barley-alfalfa-canola based diet. We amplified the V3-V5 region of 16S rRNA gene to identify the bacterial community using Roche 454 Junior system. After quality trimming, a total of 165,585 sequence reads were obtained from different segments of the small intestine (SI). A total of 701 operational taxonomic units (OTUs) were identified in the different segments of small intestine. Firmicutes (14-99%) and Proteobacteria (0.5-76%) were the most predominant bacterial phyla in the small intestine. Based on species richness estimation (Chao1 index), the average number of estimated OTUs in the small intestinal compartments were 148 in Duodenum, 167 in Jejunum, and 85 in Ileum, respectively. Low number of core OTUs identified in each compartment of small intestine across individual birds (Duodenum: 13 OTUs, Jejunum: 2 OTUs, Ileum: 14 OTUs) indicated unique bacterial community in each bird. Moreover, only 2 OTUs (Escherichia and Sinobacteraceae) were identified as core bacteria along the whole small intestine. PICRUSt analysis has indicated that the detoxification of plant material and environmental chemicals seem to be performed by SI microbiota, especially those in the jejunum. The emu cecal microbiome has more genes than SI segments involving in protective or immune response to enteric pathogens. Microbial digestion and fermentation is mostly in the jejunum and ceca. This is the first study to characterize the microbiota of different compartments of the emu intestines via gut samples and not fecal samples. Results from this study allow us to further investigate the influence of the seasonal and physiological changes of intestinal microbiota on the nutrition of emus and indirectly influence the fatty acid composition of emu fat.

Differential associations between scale-free neural dynamics and different levels of cognitive ability.

As indicators of cognitive function, scale-free neural dynamics are gaining increasing attention in cognitive neuroscience. Although the functional relevance of scale-free dynamics has been extensively reported, one fundamental question about its association with cognitive ability remains unanswered: is the association universal across a wide spectrum of cognitive abilities or confined to specific domains? Based on dual-process theory, we designed two categories of tasks to analyze two types of cognitive processes-automatic and controlled-and examined their associations with scale-free neural dynamics characterized from resting-state electroencephalography (EEG) recordings obtained from a large sample of human adults (N = 102). Our results showed that resting-state scale-free neural dynamics did not predict individuals' behavioral performance in tasks that primarily engaged the automatic process but did so in tasks that primarily engaged the controlled process. In addition, by fitting the scale-free parameters separately in different frequency bands, we found that the cognitive association of scale-free dynamics was more strongly manifested in higher-band EEG spectrum. Our findings indicate that resting-state scale-free dynamics are not universal neural indicators for all cognitive abilities but are mainly associated with high-level cognition that entails controlled processes. This finding is compatible with the widely claimed role of scale-free dynamics in reflecting properties of complex dynamic systems.

Temporally resolved neural dynamics underlying handwriting.

How do the temporal dynamics of neural activity encode highly coordinated visual-motor behaviour? To capture the millisecond-resolved neural activations associated with fine visual-motor skills, we devised a co-registration system to simultaneously record electroencephalogram and handwriting kinematics while participants were performing four handwriting tasks (writing in Chinese/English scripts with their dominant/non-dominant hand). The neural activation associated with each stroke was clearly identified with a well-structured and reliable pattern. The functional significance of this pattern was validated by its significant associations with language, hand and the cognitive stages and kinematics of handwriting. Furthermore, the handwriting rhythmicity was found to be synchronised to the brain's ongoing theta oscillation, and the synchronisation was associated with the factor of language and hand. These major findings imply an implication between motor skill formation and the interplay between the rhythms in the brain and the peripheral systems.

ICTV Virus Taxonomy Profile: Arteriviridae 2021.

The family Arteriviridae comprises enveloped RNA viruses with a linear, positive-sense genome of approximately 12.7 to 15.7 kb. The spherical, pleomorphic virions have a median diameter of 50-74 nm and include eight to eleven viral proteins. Arteriviruses infect non-human mammals in a vector-independent manner. Infections are often persistent and can either be asymptomatic or produce overt disease. Some arteriviruses are important veterinary pathogens while others infect particular species of wild rodents or African non-human primates. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Arteriviridae, which is available at ictv.global/report/arteriviridae.

First meeting in Asia of the Asia Pacific Research Integrity network.

In 2017, the University of Hong Kong and the University of California San Diego co-hosted the first Asian meeting of the recently formed Asia Pacific Research Integrity (APRI) network in Hong Kong. Aligned with planning meetings in 2015 and 2016 funded in part by the US Office of Research Integrity (ORI), the Hong Kong meeting was designed by a multi-national planning committee to address pressing challenges in research integrity: improving multi-national communication; exchanging information on managing misconduct investigations; and sharing best practices to promote research integrity. To create a sustainable, robust international partnership to promote research integrity in the region, the purpose of this 2017 meeting was to foster multi-national awareness, understanding, and opportunities for collaboration. The meeting was defined by four objectives that emerged from the previous meetings: (1) Articulate differences as well as areas of common ground; (2) Identify best or recommended practices; (3) Identify opportunities for research or collaboration; and (4) Set an APRI network agenda for coming years. The key anticipated outcome was to advance the conversation surrounding research integrity among academic institutions and regulators in Asian and Pacific Rim nations. This outcome was evidenced by meeting participation, participant satisfaction, and articulation of next steps for the APRI network.

Genetic diversity of PRRSV 1 in Central Eastern Europe in 1994-2014: origin and evolution of the virus in the region.

More than 20 years after the first outbreaks, the phylogenetic picture of PRRSV is still incomplete and full of gaps, especially in regards of PRRSV 1. Due to the exceptional diversity observed at the eastern borders of Europe and the low number of available sequences from Central Eastern European countries, the authors collected and analyzed both recent as well as already submitted sequences comparing them to a large backbone set of available ORF5 sequences representing the full spectrum of PRRSV 1 Subtype 1 diversity to conduct a systematic phylogenetic analysis and reclassification elucidating the diversity of the virus in these countries. Moreover, further analyses of the EUROSTAT data regarding the live pig movement trends revealed their influence of virus diversity and evolution. The results indicate that besides the effect of local, isolated divergent evolution and the use of modified live vaccines, the most important factor influencing a given country's virus diversity is the transboundary movement of live, infected animals.

Interaction of genotype and diet on small intestine microbiota of Japanese quail fed a cholesterol enriched diet.

Our previous study has shown that genetic selection for susceptibility/resistance to diet-induced atherosclerosis has affected the Japanese quail's cecal environment to accommodate distinctly different cecal microbiota. In this study, we fed the Atherosclerosis-resistant (RES) and -susceptable (SUS) quail a regular and a cholesterol enriched diet to examine the interaction of host genotype and diet on the diversity, composition, and metabolic functions of the duodenal and ileal microbiota with relations to atherosclerosis development. In the duodenal content, 9 OTUs (operational taxonomic units) were identified whose abundance had significant positive correlations with plasma total cholesterol, LDL level and/or LDL/HDL ratio. In the ileal content, 7 OTUs have significant correlation with plasma HDL. Cholesterol fed RES hosted significantly less Escherichia and unclassified Enterobacteriaceae (possibly pathogenic) in their duodenum than SUS fed the same diet. Dietary cholesterol significantly decreased the duodenal microbiome of SUS's biosynthesis of Ubiquinone and other terpenoid-quinone. Cholesterol fed RES had significantly more microbiome genes for Vitamin B6, selenocompound, taurine and hypotaurine, and Linoleic acid metabolism; Bisphenol degradation; primary bile acid, and butirosin and neomycin biosynthesis than SUS on the same diet. Microbiome in the ileum and ceca of RES contributed significantly towards the resistance to diet induced atherosclerosis.

Phenotypic characterization of a highly pathogenic Italian porcine reproductive and respiratory syndrome virus (PRRSV) type 1 subtype 1 isolate in experimentally infected pigs.

Highly pathogenic (HP) isolates of the PRRS virus started emerging in North America and Asia in the late 1990s. More recently, they have emerged in Europe. These isolates are characterized by high viral loads, severe general clinical signs and high mortality, in sows, weaners and growers. Their genome shows a discontinuous aminoacids deletion in the non-structural protein 2 (NSP2). The present study was aimed at characterizing the clinical, pathological and immunological features of a highly pathogenetic, Italian PRRSV-1 subtype 1 isolate (PRRSV1_PR40/2014), following experimental infection in conventional 4-weeks-old pigs. The PRRSV1_PR40/2014 infected group showed severe clinical signs (high fever and dispnoea). Pathological lesions, including severe lymphocytopenia in bronchial lymph-nodes and thymus were also recorded. Higher serum PRRSV genome copies and lower virus neutralizing antibody titer were observed in the PR40 group, when compared to the group infected with a conventional PRRSV strain. The genetic analysis of the strain, and the phenotypic features observed in the field and reproduced in the experimental study, confirmed the high pathogenicity of the Italian PRRSV-1 subtype 1 PR40 isolate.

Transmission electron microscopy artifacts in characterization of the nanomaterial-cell interactions.

We investigated transmission electron microscopy artifacts obtained using standard sample preparation protocols applied to the investigation of Escherichia coli cells exposed to common nanomaterials, such as TiO2, Ag, ZnO, and MgO. While the common protocols for some nanomaterials result only in known issues of nanomaterial-independent generation of anomalous deposits due to fixation and staining, for others, there are reactions between the nanomaterial and chemicals used for post-fixation or staining. Only in the case of TiO2 do we observe only the known issues of nanomaterial-independent generation of anomalous deposits due to exceptional chemical stability of this material. For the other three nanomaterials, different artifacts are observed. For each of those, we identify causes of the observed problems and suggest alternative sample preparation protocols to avoid artifacts arising from the sample preparation, which is essential for correct interpretation of the obtained images and drawing correct conclusions on cell-nanomaterial interactions. Finally, we propose modified sample preparation and characterization protocols for comprehensive and conclusive investigations of nanomaterial-cell interactions using electron microscopy and for obtaining clear and unambiguous revelation whether the nanomaterials studied penetrate the cells or accumulate at the cell membranes. In only the case of MgO and ZnO, the unambiguous presence of Zn and Mg could be observed inside the cells.

High fat diet induced atherosclerosis is accompanied with low colonic bacterial diversity and altered abundances that correlates with plaque size, plasma A-FABP and cholesterol: a pilot study of high fat diet and its intervention with Lactobacillus rhamnosus GG (LGG) or telmisartan in ApoE-/- mice.

BACKGROUND: Atherosclerosis appears to have multifactorial causes - microbial component like lipopolysaccharides (LPS) and other pathogen associated molecular patterns may be plausible factors. The gut microbiota is an ample source of such stimulants, and its dependent metabolites and altered gut metagenome has been an established link to atherosclerosis. In this exploratory pilot study, we aimed to elucidate whether microbial intervention with probiotics L. rhamnosus GG (LGG) or pharmaceuticals telmisartan (TLM) could improve atherosclerosis in a gut microbiota associated manner. METHODS: Atherosclerotic phenotype was established by 12 weeks feeding of high fat (HF) diet as opposed to normal chow diet (ND) in apolipoprotein E knockout (ApoE-/-) mice. LGG or TLM supplementation to HF diet was studied. RESULTS: Both LGG and TLM significantly reduced atherosclerotic plaque size and improved various biomarkers including endotoxin to different extents. Colonial microbiota analysis revealed that TLM restored HF diet induced increase in Firmicutes/Bacteroidetes ratio and decrease in alpha diversity; and led to a more distinct microbial clustering closer to ND in PCoA plot. Eubacteria, Anaeroplasma, Roseburia, Oscillospira and Dehalobacteria appeared to be protective against atherosclerosis and showed significant negative correlation with atherosclerotic plaque size and plasma adipocyte - fatty acid binding protein (A-FABP) and cholesterol. CONCLUSION: LGG and TLM improved atherosclerosis with TLM having a more distinct alteration in the colonic gut microbiota. Altered bacteria genera and reduced alpha diversity had significant correlations to atherosclerotic plaque size, plasma A-FABP and cholesterol. Future studies on such bacterial functional influence in lipid metabolism will be warranted.

Toxicity of ZnO and TiO2 to Escherichia coli cells.

We performed a comprehensive investigation of the toxicity of ZnO and TiO2 nanoparticles using Escherichia coli as a model organism. Both materials are wide band gap n-type semiconductors and they can interact with lipopolysaccharide molecules present in the outer membrane of E. coli, as well as produce reactive oxygen species (ROS) under UV illumination. Despite the similarities in their properties, the response of the bacteria to the two nanomaterials was fundamentally different. When the ROS generation is observed, the toxicity of nanomaterial is commonly attributed to oxidative stress and cell membrane damage caused by lipid peroxidation. However, we found that significant toxicity does not necessarily correlate with up-regulation of ROS-related proteins. TiO2 exhibited significant antibacterial activity, but the protein expression profile of bacteria exposed to TiO2 was different compared to H2O2 and the ROS-related proteins were not strongly expressed. On the other hand, ZnO exhibited lower antibacterial activity compared to TiO2, and the bacterial response involved up-regulating ROS-related proteins similar to the bacterial response to the exposure to H2O2. Reasons for the observed differences in toxicity and bacterial response to the two metal oxides are discussed.

Triterpenoid herbal saponins enhance beneficial bacteria, decrease sulfate-reducing bacteria, modulate inflammatory intestinal microenvironment and exert cancer preventive effects in ApcMin/+ mice.

Saponins derived from medicinal plants have raised considerable interest for their preventive roles in various diseases. Here, we investigated the impacts of triterpenoid saponins isolated from Gynostemma pentaphyllum (GpS) on gut microbiome, mucosal environment, and the preventive effect on tumor growth. Six-week old ApcMin/+ mice and their wild-type littermates were fed either with vehicle or GpS daily for the duration of 8 weeks. The fecal microbiome was analyzed by enterobacterial repetitive intergenic consensus (ERIC)-PCR and 16S rRNA gene pyrosequencing. Study showed that GpS treatment significantly reduced the number of intestinal polyps in a preventive mode. More importantly, GpS feeding strikingly reduced the sulfate-reducing bacteria lineage, which are known to produce hydrogen sulfide and contribute to damage the intestinal epithelium or even promote cancer progression. Meanwhile, GpS also boosted the beneficial microbes. In the gut barrier of the ApcMin/+ mice, GpS treatment increased Paneth and goblet cells, up-regulated E-cadherin and down-regulated N-cadherin. In addition, GpS decreased the pro-oncogenic ß-catenin, p-Src and the p-STAT3. Furthermore, GpS might also improve the inflamed gut epithelium of the ApcMin/+ mice by upregulating the anti-inflammatory cytokine IL-4, while downregulating pro-inflammatory cytokines TNF-α, IL-1ß and IL-18. Intriguingly, GpS markedly stimulated M2 and suppressed M1 macrophage markers, indicating that GpS altered mucosal cytokine profile in favor of the M1 to M2 macrophages switching, facilitating intestinal tissue repair. In conclusion, GpS might reverse the host's inflammatory phenotype by increasing beneficial bacteria, decreasing sulfate-reducing bacteria, and alleviating intestinal inflammatory gut environment, which might contribute to its cancer preventive effects.

[Screening and genomic analysis of a lignocellulose degrading bacterium].

Objective: This study is aimed to screen and identify a bacterium with the ability to degrade lignocellulose, to perform its genomic analysis, and to determine its related enzymatic activities. Methods: Using a bleaching/dyeing method with three kinds of lignin analogues (Azure-B; Phenol red; Guaiacol), we separated and screened a bacterium strain, with a strong ability to degrade lignocellulose, from soil enriched by decaying wood and leaves. We identified the species of this bacterium according to its 16S rRNA gene and core gene sequence analysis. In order to understand the trend of enzymatic activities within a certain period, we used ultraviolet spectrophotometry on manganese peroxidase (MnP), laccase (Lac), carboxymethyl cellulose (CMCase) and filter paper (FPA). The whole genome was sequenced by Illumina MiSeq and 454 GS Junior platforms. The protein sequences were annotated from the whole genome and compared with COG and KEGG databases through BLASTp to determine several potential lignocellulose-degrading enzymes and pathways. Some of the annotated genes were further verified by realtime RT-PCR. Results: We obtained strain S12 which was identified as Raoultella ornithinolytica. The bacterium grew to stationary phase after being incubated in CMC-Na liquid medium for 28 h, at which its cellulose degradation related enzymatic activities reached to peak values. Bioinformatic analysis results showed that strain S12 has some significant genes that encode enzymes working in the lignin degradation pathway, such as peroxidase, Fe-Mn superoxide dismutase, catechol 1,2-dioxygenase, protocatechuate 3, 4-dioxygenase, etc. The expression levels of these genes were higher when strain S12 was grown in a medium with lignin as the unique carbon source than in a medium with glucose as the unique carbon source. Also, strain S12 has a complete cellulose degradation and ethanol generation pathway. Conclusion: Raoultella ornithinolytica S12 has the ability to degrade lignocellulose effectively, which is significant in promoting the development of the lignocellulose application industry.

Complete Genome Sequence of Klebsiella pneumoniae Strain HKUOPLC, a Cellulose-Degrading Bacterium Isolated from Giant Panda Feces.

We report here the complete genome sequence of Klebsiella pneumoniae strain HKUOPLC, isolated from a giant panda fecal sample collected from Ocean Park, Hong Kong. The complete genome of this bacterium may contribute to the discovery of efficient cellulose-degrading pathways.

Pyrosequencing of the bacteria associated with Platygyra carnosus corals with skeletal growth anomalies reveals differences in bacterial community composition in apparently healthy and diseased tissues.

Corals are rapidly declining globally due to coral diseases. Skeletal growth anomalies (SGA) or "coral tumors" are a group of coral diseases that affect coral reefs worldwide, including Hong Kong waters in the Indo-Pacific region. To better understand how bacterial communities may vary in corals with SGA, for the first time, we examined the bacterial composition associated with the apparently healthy and the diseased tissues of SGA-affected Platgyra carnosus using 16S ribosomal rRNA gene pyrosequencing. Taxonomic analysis revealed Proteobacteria, Bacteroidetes, Cyanobacteria, and Actinobacteria as the main phyla in both the apparently healthy and the diseased tissues. A significant difference in the bacterial community composition was observed between the two conditions at the OTU level. Diseased tissues were associated with higher abundances of Acidobacteria and Gemmatimonadetes, and a lower abundance of Spirochaetes. Several OTUs belonging to Rhodobacteraceae, Rhizobiales, Gammaproteobacteria, and Cytophaga-Flavobacterium-Bacteroidetes (CFB) were strongly associated with the diseased tissues. These groups of bacteria may contain potential pathogens involved with the development of SGA or opportunistic secondary or tertiary colonizers that proliferated upon the health-compromised coral host. We suggest that these bacterial groups to be further studied based on inoculation experiments and testing of Koch's postulates in efforts to understand the etiology and progression of SGA.

The effect of diet and host genotype on ceca microbiota of Japanese quail fed a cholesterol enriched diet.

Two Japanese quail strains, respectively atherosclerosis-susceptible (SUS) and -resistant (RES), have been shown to be good models to study cholesterol metabolism and transportation associated with atherosclerosis. Our objective was to examine possible difference in cecal microbiota between these strains when fed a control diet and a cholesterol enriched diet, to determine how host genotype and diet could affect the cecal microbiome that may play a part in cholesterol metabolism. A factorial study with both strains and two diets (control, cholesterol) was carried out. Cecal content was collected from 12 week old quail that have been on their respective diets for 6 weeks. DNA was extracted from the samples and the variable region 3-5 of the bacterial 16S rRNA gene was amplified. The amplicon libraries were subjected to pyrosequencing. Principal Component Analysis (PCA) of ß-diversity showed four distinct microbiota communities that can be assigned to the 4 treatment groups (RES/control, RES/cholesterol, SUS/control, SUS/cholesterol). At the Phylum level, the 4 treatment groups has distinct Firmicutes community characteristics but no significant difference in Bacteroidetes. Eubacterium dolichum was rare in RES/control but became overabundant in RES/cholesterol. An unclassified species of Lactobacillaceae was found in abundance in SUS/control but the same species was rare in RES/cholesterol. On the other hand, two Lactobacillus species were only found in RES/control and an unclassified Lachnospiraceae species was abundant in RES/cholesterol but rare in SUS/control. The abundance of four species of Lachnospiraceae, three species of Ruminococcaceae and one species of Coprobacillaceae was positively correlated with plasma Total Cholesterol, plasma LDL, and LDL/HDL ratio. Our study of cecal microbiota in these quail has demonstrated that selection for susceptibility/resistance to diet induced atherosclerosis has also affected the quail's cecal environment to host distinctly different cecal microbiome.

Complete Genome Sequence of Klebsiella variicola Strain HKUOPLA, a Cellulose-Degrading Bacterium Isolated from Giant Panda Feces.

We report here the complete genome sequence of Klebsiella variicola strain HKUOPLA, isolated from a giant panda feces sample collected from Ocean Park, Hong Kong. The complete genome of this bacterium may contribute toward the discovery of efficient cellulose-degrading pathways.

Metal oxide nanoparticles with low toxicity.

A number of different nanomaterials produced and incorporated into various products are rising. However, their environmental hazards are frequently unknown. Here we consider three different metal oxide compounds (SnO2, In2O3, and Al2O3), which have not been extensively studied and are expected to have low toxicity. This study aimed to comprehensively characterize the physicochemical properties of these nanomaterials and investigate their toxicity on bacteria (Escherichia coli) under UV illumination and in the dark, as well as on a marine diatom (Skeletonema costatum) under ambient illumination/dark (16-8h) cycles. The material properties responsible for their low toxicity have been identified based on comprehensive experimental characterizations and comparison to a metal oxide exhibiting significant toxicity under illumination (anatase TiO2). The metal oxide materials investigated exhibited significant difference in surface properties and interaction with the living organisms. In order for a material to exhibit significant toxicity, it needs to be able to both form a stable suspension in the culture medium and to interact with the cell walls of the test organism. Our results indicated that the observed low toxicities of the three nanomaterials could be attributed to the limited interaction between the nanoparticles and cell walls of the test organisms. This could occur either due to the lack of significant attachment between nanoparticles and cell walls, or due to their tendency to aggregate in solution.