Spore Clusters Research Articles

Transcriptomic Approach Reveals Contrasting Patterns of Differential Gene Expression during Tannin Biodegredation by Aspergillus tubingensis in Liquid and Solid Cultures

Tannins, one of the most common anti-nutritional factors in feed, can be effectively degraded by various enzymes secreted by Aspergillus tubingensis (A. tubingensis). The cultivation method of fungi significantly impacts gene expression, which influences the production of enzymes and metabolites. In this study, we analyzed the tannin biodegredation efficiency and the transcriptomic responses of A. tubingensis in liquid and solid cultures with tannin added. The observed morphology of A. tubingensis resembled typical fungal hyphae of mycelium submerged and grown in liquid cultures, while mainly spore clusters were observed in solid cultures. Furthermore, the tannin biodegredation efficiency and protein secretion of A. tubingensis in liquid cultures were significantly higher than in solid cultures. Additionally, 54.6% of the 11,248 differentially expressed genes were upregulated in liquid cultures, including AtWU_03490 (encoding ABC multidrug transporter), AtWU_03807 (ribonuclease III), AtWU_10270 (peptidyl-tRNA hydrolase), and AtWU_00075 (arabinogalactan endo-1,4-beta-galactosidase). Functional and gene ontology enrichment analyses indicated upregulation in processes including oxidation reduction, drug metabolism, and monocarboxylic acid metabolism. Overall, this study provides insight into the transcriptomic response to tannin biodegradation by A. tubingensis in different cultures and reveals that liquid cultures induce greater transcriptomic variability compared to solid cultures.

Tinea versicolor: an updated review.

Tinea versicolor is a common superficial fungal infection of the skin with various clinical manifestations. This review aims to familiarize physicians with the clinical features, diagnosis and management of tinea versicolor. A search was conducted in July 2022 in PubMed Clinical Queries using the key terms "tinea versicolor" OR "pityriasis versicolor". The search strategy included all clinical trials, observational studies and reviews published within the past 10 years. Tinea versicolor is caused by Malassezia species, notably M. globosa, M. furfur and M. sympodialis. The condition is characterized by scaly hypopigmented or hyperpigmented macules/patches, primarily located on the upper trunk, neck and upper arms. The diagnosis is usually based on characteristic clinical features. If necessary, a potassium hydroxide preparation test can be performed to reveal numerous short, stubby hyphae intermixed with clusters of spores. Most patients with tinea versicolor respond to topical antifungal therapy, which has a better safety profile (fewer adverse events, fewer drug interactions) and lower cost compared to systemic treatment and is therefore the treatment of choice. Oral antifungal therapy is typically reserved for patients with extensive disease, frequent recurrences or disease that is refractory to topical therapy. Advantages of oral antifungal therapy include increased patient compliance, shorter duration of treatment, increased convenience, less time involved with therapy and reduced recurrence rates. On the other hand, oral antifungal therapy is associated with higher cost, greater adverse events and potential drug-drug interactions and is therefore not the first-line treatment for tinea versicolor. Long-term intermittent prophylactic therapy should be considered for patients with frequent recurrence of the disease. Selection of antifungal agents depends on several factors, including efficacy, safety, local availability, ease of administration, likelihood of compliance and potential drug interactions of the antifungal agent.

Colletotrichum coccodes causing “black dot” of sugar beet in the Pacific Northwest of the USA

Sugar beet (Beta vulgaris) is an important sugar crop in temperate regions. In 2014, sugar beet roots in Washington and Oregon, U.S.A. were found with a shallow, firm, dark rot with minute black “dots” within the tissue (Figs. 1, 2), similar to “black dot” on potato (Davis & Johnson, 2001). Symptoms were observed in freshly harvested roots in the processing factory. Diseased tissue was surface disinfected with 10% bleach, plated on 2% water agar and incubated at room temperature with ambient lighting. All visible growth from ten tissue pieces (five per beet, one each from Washington and Oregon) was fungal, with hyaline mycelia and numerous dark, spherical sclerotia. Pure cultures were obtained by hyphal tip transfer to malt extract agar (MEA), incubated for seven days in the light at room temperature, and examined for morphological characteristics. Yellow spore clusters with dark setae were observed in culture. Conidia (20-25 × 3–4 µm) were hyaline and straight with evenly rounded ends (Fig. 3) matching those of Colletotrichum coccodes (Chesters & Hornby, 1965). For molecular characterisation, DNA was extracted from seven-day old cultures using a CTAB protocol (Anonymous, 2009). PCR amplification used an Invitrogen High Fidelity PCR mix (Thermo Fisher Scientific Inc., Waltham, USA) with primers ITS1 and ITS4 (White et al., 1990) and the resulting amplicons were sequenced by Sanger sequencing. A BLASTn search with the sequence of isolate Co14-1 (GenBank Accession No. KX011522) showed a 99% identity to CBS369.75 (HM171679), the type strain for C. coccodes (Cannon et al., 2012) as well as to additional C. coccodes isolates (JX294043, JX205194, JX205192, and KJ744346). As initial samples were found at harvest, healthy roots of two sugar beet germplasm (C869 and SR102) that had been grown in the field for five months at the Saginaw Valley Research and Education Center (Frankenmuth, Michigan, USA) were used for pathogenicity testing. After removal from the field, roots were kept at 7°C for one-two months then planted in potting mix and grown in a greenhouse at 22°C ±4°C. After growth of new leaves was visible, two plants of each germplasm were treated with a 10 ml drench of a 103 spores/ml suspension that was produced by growing isolate Co14-1 on MEA for seven-ten days, flooding the surface with sterile distilled water, and dislodging the spores with a sterile plastic cell spreader. Plants were grown for four weeks after inoculation and evaluated. Roots of inoculated plants showed shallow sunken lesions with minute black “dots” similar to those on the initial samples (Fig. 4). A fungus morphologically identified as C. coccodes was isolated from lesions on all inoculated beets, completing Koch's postulates. No Colletotrichum sp. was isolated from control beets. The trial was conducted twice with the same results. To our knowledge this is the first report of C. coccodes on sugar beet from the field. Although there was little root loss observed on beet, black dot infection can impact storage in potato (Davis & Johnson 2001). Therefore, testing the potential impact of black dot on storage of sugar beet is warranted. The authors would like to thank Tom Goodwill for his technical assistance.

Absorption of ultraviolet radiation in bacterial spores in clusters in air and on surfaces: Model calculations using the multi-sphere T-Matrix method

Ultraviolet (UV) germicidal irradiation (UVGI) is used to inactivate viruses and kill other microbes to decrease transmission of disease. Microbes such as bacterial spores can occur within clusters of spores or other particles. Such particles, in air or in water, can in some cases partially shield spores within them from UVGI, whether on a surface or suspended. There is a need to better understand how such shielding varies with particle size, composition, and illumination angle. Here the Multi-Sphere T-Matrix (MSTM) method is used to model the absorption of UVGI by bacterial spores in clusters, where each spore is approximated as a homogeneous sphere. The clusters of spores may be surrounded only by air or may be within an encompassing “host” sphere in air. Calculated results of the UV absorption efficiencies for each spore are illustrated for clusters of 54 spores within host spheres of different optical properties, on surfaces with different compositions (polycarbonate, iron and aluminum), and for illumination with UV light from different directions with respect to the cluster and the surface. For the solar UV wavelengths 302 and 325 nm and the deep purple 450 nm, and the unpigmented bacteria modeled here, the penetration depths in both the spores and host sphere are so much larger than the cluster and host sphere size (5.08 µm) that the general effect on the absorption by spores is relatively insensitive to wavelength. Results at 266 nm suggest that in using and validating UVGI for inactivation, the sizes and compositions of the particles are important.

Clonal spore populations in sporocarps of arbuscular mycorrhizal fungi.

Some arbuscular mycorrhizal (AM) fungal species known to form sporocarps (i.e., aggregations of spores) are polyphyletic in two orders, Glomerales and Diversisporales. Spore clusters (sporocarp-like structures) often formed in pot cultures or in vitro conditions are supposed to be clonal populations, while sporocarps in natural habitats with a fungal peridium are morphologically similar to those of epigeous sexual (zygosporic) sporocarps of Endogone species. Thus, in this study, we explored the genetics of sporocarpic spores of two AM fungi with a view to possibilities of clonal or sexual reproduction during sporocarps formation. To examine these possibilities, we investigated single-nucleotide polymorphisms (SNPs) in reduced genomic libraries of spores isolated from sporocarps molecularly identified as Rhizophagus irregularis and Diversispora epigaea. In addition, partial sequences of the MAT locus HD2 gene of R. irregularis were phylogenetically analyzed to determine the nuclear status of the spores. We found that most SNPs were shared among the spores isolated from each sporocarp in both species. Furthermore, all HD2 sequences from spores isolated from three R. irregularis sporocarps were identical. These results indicate that those sporocarps comprise clonal spores. Therefore, sporocarps with clonal spores may have different functions than sexual reproduction, such as massive spore production or spore dispersal via mycophagy.

Hydrophobicity of abiotic surfaces governs droplets deposition and evaporation patterns

Surface contamination with droplets containing bacteria is of concern in the food industry and other environments where hygiene control is essential. Deposition patterns after the drying of contaminated droplets is affected by numerous parameters. The present study evaluated the rate of evaporation and the shape of deposition patterns after the drying of water droplets on a panel of materials with different surface properties (topography, hydrophobicity). The influence of the particle properties (in this study 1 μm-microspheres and two bacterial spores) was also investigated. Polystyrene microspheres were hydrophobic, while Bacillus spores were hydrophilic or hydrophobic, and surrounded by different surface features. In contrast to material topography, hydrophobicity was shown to deeply affect droplet evaporation, with the formation of small, thick deposits with microspheres or hydrophilic spores. Among the particle properties, the spore morphology (size and round/ovoid shape) did not clearly affect the deposition pattern. Conversely, hydrophobic spores aggregated to form clusters, which quickly settled on the materials and either failed to migrate, or only migrated to a slight extent on the surface, resulting in a steady distribution of spores or spore clusters over the whole contaminated area.Adherent bacteria or spores are known to be highly resistant to many stressful environmental conditions. In view of all the quite different patterns obtained following drying of spore-containing droplets, it seems likely that some of these would entail enhanced resistance to hygienic processes.

Where is the machine looking? Locating discriminative light-scattering features by class-activation mapping

We explore a technique called class-activation mapping (CAM) to investigate how a Machine Learning (ML) architecture learns to classify particles based on their light-scattering signals. We release our code, and also find that different regions of the light-scattering signals play different roles in ML classification. These regions depend on the type of particles being classified and on the nature of the data obtained and trained. For instance, the Mueller-matrix elements S11*,S12* and S21*had the greatest classification activation in the diffraction region. Linear polarization elements S12* and S21* were most accurate in the backscattering region for clusters of spheres and spores, and was most accurate in the diffraction region for other particle classes. The CAM technique was able to highlight light-scattering angles that maximize the potential for discrimination of similar particle classes. Such information is useful for designing detector systems to classify particles where limited space or resources are available, including flow cytometry and satellite remote sensing.

Nanoglomus plukenetiae, a new fungus from Peru, and a key to small-spored Glomeraceae species, including three new genera in the “Dominikia complex/clades”

A new arbuscular mycorrhizal fungus was found in an agricultural plantation of Plukenetia volubilis, the inka nut (also called “sacha inchi” or “inka peanut”) in the Amazonia region of San Martin State in Peru. In this site, the inka nut was grown in mixed cultures together with Zea mays and Phaseolus vulgaris. The fungus was propagated in bait and single-species cultures on Sorghum vulgare, Brachiaria brizantha, Medicago sativa, and Plukenetia volubilis as host plants. The fungus differentiates hyaline spores terminally or intercalary on cylindrical to slightly funnel-shaped hyphae, singly or in spore clusters with up to ca. 90 spores per cluster. The spores are bi-layered, (20–)25–36(–45) μm in diameter and show regularly a visible septum at the spore base, despite the small spore and tiny hyphae sizes. Phylogenetically, the new fungus represents a new genus in a separated clade, near to the already known Dominikia clades. It can be distinguished from other species by the small spore size, the characteristics of the spore wall layers, and the clearly visible septum at the spore base, which in Kamienskia and Microkamienskia species has rarely to never been reported, while Dominikia species usually have a higher variability of spore sizes and spore wall characteristics. The fungus is here described under the epithet Nanoglomus plukenetiae, serving as type species of the new genus Nanoglomus. The revision of the species and environmental sequences in the Dominikia clades, based on both morphological and molecular phylogenetic analyses, revealed at least two other new genera: Microdominikia gen. nov., based on D. litorea, and Orientoglomus gen. nov., based on D. emiratia. Finally, in the present study, a key for all small-spored species in the Glomeraceae is included comprising all known Dominikia, Kamienskia, Microdominikia, Microkamienskia, Nanoglomus, Orientoglomus spp., and all small-spored Rhizoglomus spp.

Microkamienskia gen. nov. and Microkamienskia peruviana, a new arbuscular mycorrhizal fungus from Western Amazonia

A new arbuscular mycorrhizal (AM) fungus, Microkamienskia peruviana, was detected in bait cultures for arbuscular mycorrhizal fungi established with rhizospheric soil substrates of the inka nut (Plukenetia volubilis). The field soil derived from three agricultural plantations in the Amazonia lowlands of the province Lamas, San Martin State, in Peru. The fungus was subsequently propagated in single species cultures on Sorghum sp., Brachiaria sp.,Medicago sativa and P. volubilis as host plants. The new species differentiates hyaline spores regularly in spore clusters, up to 500–800×400–600 μm. The spores are 16–31(–36)×13–29(–35) μm in diam, formed on cylindrical or slightly funnel-shaped hyphae, without a septum at or close to the spore base. Phylogenetically, the new fungus belongs to a new genus, named Microkamienskia, which has as type species M. perpusilla comb. nov. and to which also M. divaricata comb. nov. belongs. Both are transferred from Kamienskia to Microkamienskia in the present study. The new fungus can be identified by the ballooning semi-persistent to evanescent outer spore wall layer in PVLG-based mountants that is not known for the other species of these two genera, nor for any other glomeromycotan species of similar small spore sizes. Kamienskia and Microkamienskia species can be distinguished by their position in the phylogenetic tree and by hyaline spores, open pores at the spore bases and in the subtending hyphae, and by their spore sizes that are for Microkamienskia among the smallest spore sizes so far detected for AM fungi (15–35 μm).

Rhizoglomus venetianum, a new arbuscular mycorrhizal fungal species from a heavy metal-contaminated site, downtown Venice in Italy

Rhizoglomus venetianum, a new arbuscular mycorrhizal fungal species, has been isolated and propagated from a heavy metal-contaminated site in Sacca San Biagio island, downtown Venice, Italy. Interestingly, under the high levels of heavy metals occurring in the site, the new fungus was able to grow only intraradically. In greenhouse trap and single species cultures under low heavy metal levels, the fungus produced innumerous spores, clusters, and sporocarps extraradically, which were formed terminally on subtending hyphae either singly, in small spore clusters, or, preferably, in loose to compact non-organized sporocarps up to 2500 × 2000 × 2000 μm. Spores are golden-yellow to bright yellow brown, globose to subglobose to rarely oblong, 75–145 × 72–140 μm in diameter, and have four spore wall layers. Morphologically, the new fungus is similar to R. intraradices, and phylogenetically, it forms a monophyletic clade next to R. irregulare, which generally forms irregular spores and lacks, like R. intraradices, the flexible innermost wall layer beneath the structural/persistent third wall layer. A key for the species identification is presented comprising all 18 Rhizoglomus species, so far described or newly combined.

Infrared Extinction Performance of Randomly Oriented Microbial-Clustered Agglomerate Materials.

In this study, the spatial structure of randomly distributed clusters of fungi An0429 spores was simulated using a cluster aggregation (CCA) model, and the single scattering parameters of fungi An0429 spores were calculated using the discrete dipole approximation (DDA) method. The transmittance of 10.6 µm infrared (IR) light in the aggregated fungi An0429 spores swarm is simulated by using the Monte Carlo method. Several parameters that affect the transmittance of 10.6 µm IR light, such as the number and radius of original fungi An0429 spores, porosity of aggregated fungi An0429 spores, and density of aggregated fungi An0429 spores of the formation aerosol area were discussed. Finally, the transmittances of microbial materials with different qualities were measured in the dynamic test platform. The simulation results showed that the parameters analyzed were closely connected with the extinction performance of fungi An0429 spores. By controlling the value of the influencing factors, the transmittance could be lower than a certain threshold to meet the requirement of attenuation in application. In addition, the experimental results showed that the Monte Carlo method could well reflect the attenuation law of IR light in fungi An0429 spore agglomerates swarms.

Phenotypic variability and community interactions of germinating Streptomyces spores

A case can be made for stochastic germination and interactions among germinating spores as beneficial germination strategies in uncertain environments. However, there is little data on how widespread, species-specific or diverse such phenomena are. Focusing on Streptomycetes, a platform was developed for quantification of germination and early growth within communities of spores. We found that the germination process is stochastic at three levels: spores vary in their germination times, mycelium networks grow at different rates, and a fraction of germlings stall their growth shortly after germination. Furthermore, by monitoring how these stochastic properties are affected by spore density and chemicals released from spores, germination interactions were quantified for four species. Stochastically germinating spores were frequently promoted or inhibited by compounds released by spores from the same or different species, and all species had distinct interaction profiles. The spatial distribution patterns were important with clusters of spores behaving differently than individual spores. Aged spores exhibited higher dormancy but could efficiently geminate in the presence of chemicals released during germination. All interactions were specific to germination and only weakly affected growth rates. This work suggests that stochastic germination is commonly affected by the community context and species have adapted diverse germination strategies.

Modeling ultraviolet dose–response ofBacillusspore clusters in air

ABSTRACTThis article presents a new way to model the narrow band ultraviolet (UV-C, 254.7 nm) radiation dose–response behavior of Bacillus spores in clusters based on knowledge of the UV-C dose–response behavior of the single spores. The approach is demonstrated using experimentally obtained survival rates for Bacillus atrophaeus var. globigii (BG) spores and BG spore clusters of several sizes exposed to UV-C fluence when aerosolized and when deposited on dry surfaces. These results are modeled to derive predicted survival rates for spores in clusters of arbitrary cluster diameter under similar conditions. The essential feature of the approach is accurate accounting for attenuation of incident UV fluence within the spore cluster to derive the fluence incident on individual spores within the cluster. The results suggest that UV fluence attenuation by bacterial spores may increase with increasing fluence, a phenomenon that has not been previously reported for bacterial spores. The results are of utility in ...

Deciphering interfungal relationships in the 410-million-yr-old Rhynie chert: Sporocarp formation in glomeromycotan spores

Fungi today enter into relationships with other fungi in many ways. Although this was likely also the case in the geologic past, detailed descriptions of interfungal associations and interactions based on fossils remain scarce. Sporocarps bounded by a peridium-like envelope occur singly within the lumen of large glomeromycotan spores (Palaeomyces gordonii var. major) from the Lower Devonian Rhynie chert. The envelope consists of multi-branched, interlacing hyphae. At the tips of hyphae extending from the envelope into the lumen are produced spheroidal to urn-shaped spores. Similar sporocarps are found in several present-day species in the Glomeraceae. Clusters of spores, superficially resembling sporocarps, may also form within dead spores from any member of the Glomeromycota, including non-sporocarpic groups such as Ambispora, Acaulospora, and the Gigasporaceae, probably because they provide a shielded or otherwise advantageous environment for sporulation. The sporocarps in P. gordonii var. major from the Rhynie chert provide important information for reconstructing the numerous levels of fungal associations and interactions that existed in early continental ecosystems.

Quantitative Analysis of Effects of UV Exposure and Spore Cluster Size on Deposition and Inhalation Hazards ofBacillusSpores

Reviews of the effects of solar UV radiation on the survival rate of aerosolized biological material found that the current understanding of environmental viability degradation in response scenarios is insufficient to inform appropriate emergency response measures. We evaluated the effects of UV degradation, in terms of the number of viable, culture forming units as a function of spore cluster size on the downwind hazard presented by a release of a biological organism such as Bacillus anthracis into the environment. We used experimentally derived survival rates for B. atrophaeus var. globigii (BG) spores and BG spore clusters (as a surrogate for Bacillus anthracis) of various sizes exposed to UVC fluences to derive predicted survival rates for single spores and spore clusters of up to 10 µm. For the range of weather conditions encountered in hazard estimates, as characterized by Pasquill-Gifford-Turner classes, we calculated and compared the downwind inhalation and deposition hazards for single spores ver...

Ortholinea saudii sp. nov. (Myxosporea: Ortholineidae) in the kidney of the marine fish Siganus rivulatus (Teleostei) from the Red Sea, Saudi Arabia.

Myxozoans, a diverse group of microscopic obligate endoparasites, can cause diseases in a number of economically important fish, including the marbled spinefoot Siganus rivulatus. To date, only 1 myxozoan, Zschokkella helmii, has been reported to infect S. rivulatus. Here we describe another myxozoan detected in S. rivulatus. Investigations of 40 marbled spinefoot fish caught from the Red Sea coast, Jeddah, Saudi Arabia, revealed clusters of parasitic spores in the kidney. Light microscope examination of the native spores revealed sub-spherical, mature spores with smooth shell valves. The 2 polar capsules were equal in size, and the polar filament was perpendicular to the longitudinal axis of the polar capsules. Histopathological examinations of the infected kidneys demonstrated the presence of both spores and developmental stages in the lumen of the renal tubules without any pathological effect. Electron microscopy investigations showed maturing spores composed of 2 valvogenic cells, each with a prominent nucleus. The valvogenic cells enclosed 2 polar capsules containing 3 filament coils as well as a binucleated sporoplasm cell filling the space between and beneath the 2 polar capsules. BLAST search analysis of the amplified sequence from the detected parasite indicated a high percent of identity to the 18S rDNA genes of different myxosporean species. Phylogenetic analysis placed the detected parasite within a clade of Ortholinea sp. (AL-2006). Based on the results of the light and electron microscopy, histopathological, and molecular investigations, the detected parasite was identified as a myxosporean parasite belonging to the genus Ortholinea and designated as O. saudii sp. nov.

Comparison of models and measurements of angle-resolved scatter from irregular aerosols

We have developed and validated a method for modeling the elastic scattering properties of biological and inert aerosols of irregular shape at near- and mid-wave infrared wavelengths. The method, based on Gaussian random particles, calculates the ensemble-average optical cross section and Mueller scattering matrix, using the measured aerodynamic size distribution and previously-reported refractive index as inputs. The utility of the Gaussian particle model is that it is controlled by only two parameters (σ and Γ) which we have optimized such that the model best reproduces the full angle-resolved Mueller scattering matrices measured at λ=1.55µm in the Standoff Aerosol Active Signature Testbed (SAAST). The method has been applied to wet-generated singlet biological spore samples, dry-generated biological spore clusters, and kaolin. The scattering computation is performed using the Discrete Dipole Approximation (DDA), which requires significant computational resources, and is thus implemented on LLGrid, a large parallel grid computer. For the cases presented, the best fit Gaussian particle model is in good qualitative correspondence with microscopy images of the corresponding class of particles. The measured and computed cross sections agree well within a factor of two overall, with certain cases bearing closer correspondence. In particular, the DDA reproduces the shape of the measured scatter function more accurately than Mie predictions. The DDA-computed depolarization factors are also in good agreement with measurement.

UV-C Decontamination of Aerosolized and Surface-Bound Single Spores and Bioclusters

Biological particles are rarely individual organisms, but are clusters of organisms physically bound to one another, or bound to other material present in the environment. The size and composition of these bioclusters contribute to the protection of the organisms within the core of cluster from the harmful effects of ambient UV light. The use of ultraviolet irradiation has been evaluated in the past as an option for decontaminating surfaces and air; however, previous studies were conducted with single spores, or poorly characterized polydispersed aerosols making comparisons between studies difficult. This study is intended to evaluate the effect of UV-C irradiation on monodispersed particles of spore clusters with mean diameters of 2.8 μm and 4.4 μm, and single spores of Bacillus atrophaeus var. globigii on fixed surfaces and as aerosol. The D90, the UV-C irradiation doses at which 90% of the colony forming units were rendered nonculturable, for single spores and spore clusters of 2.8 and 4.4 μm on surfac...

English

Root samples and rhizosphere soil of nine acacia species (Acacia abyssinica, Faidherbia albida, A. nilotica, A. senegal, A. seyal, A. sieberiana, A. saligna, A. tortilis and A. robusta) were collected from Bishoftu, Zeway and Addis Ababa sites with different land use types to assess their Arbuscular Mycorrhizal Fungal (AMF) diversity, spore density and root colonization. The percentage of root length colonized by AMF was estimated. Spores, spore clusters and sporocarps extracted from soil samples were counted and morphologically identified to species or specific morphotype. Roots of all acacia species were colonized from low to moderate or relatively high levels by AMF with the occurrence of arbuscules, vesicles and hyphae. Arbuscules were however not detected in roots of A. senegal. The highest AM fungal colonization was found in A. seyal (67.3%) from open grazing field (OGF) at Zeway followed by A. nilotica (44%), whereas the lowest AMF colonization of 12% was recorded in A. saligna at Bishoftu. Rhizosphere soils harbored AMF fungal spores ranging from 3.7 spores g-1 soil in A. nilotica to 15.0 spores g-1 in A. seyal from open grazing field (OGF) at Zeway. A total of 41 AMF species in 14 genera and 7 families of the Glomeromycota were identified. Nine species belonged to Acaulospora, 6 to Funneliformis, 4 each to Gigaspora, Glomus, and Rhizophagus, 3 each to Claroideoglomus, and Scutellospora, 2 each to Racocetra and Diversispora, and 1 each to Entrophospora, Sclerocystis, Paraglomus and Pacispora. Moreover, 2 unidentified morphotypes each of Glomus, and Acaulospora and 1 of Archaeospora were isolated. Based on relative abundance and isolation frequency of spores, C. claroideum, C. etunicatum, C. luteum, F. geosporus and G. aggregatum were the dominant species in the study. The study showed that the acacia species were characterized by relatively high AMF colonization and very high AMF diversity. AMF spore density and AM root colonization in acacia roots were influenced by soil factors such as available P and soil texture. Key words: Acaulospora, AM colonization, Arbuscules, Funneliformis, Glomeromycota, Rhizosphere soils.

Selective Weighing of Individual Microparticles Using a Hybrid Micromanipulator-Nanomechanical Resonator System

We report a system based on a combination of a micromanipulator and a cantilever-based differential resonator for selecting and weighing individual micro-scale particles. Instead of relying on probabilistic attachment of particles on sensor surfaces, the system can specifically select and weigh individual micro-entities. The micromanipulator is able to move particles from a native media to the surface of a resonator that can weigh particles with pg-level resolution. The system allows individually manipulating and weighing a wide variety of entities that can be visualized under a microscope, ranging from cell spheres to spore clusters and single diatom algae.