Root induced changes of effective 1D hydraulic properties in a soil column

Aims

Roots are essential drivers of soil structure and pore formation. This study aimed at quantifying root induced changes of the pore size distribution (PSD). The focus was on the extent of clogging vs. formation of pores during active root growth.

Methods

Parameters of Kosugi’s lognormal PSD model were determined by inverse estimation in a column experiment with two cover crops (mustard, rye) and an unplanted control. Pore dynamics were described using a convection–dispersion like pore evolution model.

Results

Rooted treatments showed a wider range of pore radii with increasing volumes of large macropores >500 μm and micropores <2.5 μm, while fine macropores, mesopores and larger micropores decreased. The non-rooted control showed narrowing of the PSD and reduced porosity over all radius classes. The pore evolution model accurately described root induced changes, while structure degradation in the non-rooted control was not captured properly. Our study demonstrated significant short term root effects with heterogenization of the pore system as dominant process of root induced structure formation.

Conclusions

Pore clogging is suggested as a partial cause for reduced pore volume. The important change in micro- and large macropores however indicates that multiple mechanic and biochemical processes are involved in root-pore interactions.     

Two new species of <Emphasis Type="Italic">Coltricia</Emphasis> (Hymenochaetaceae,Basidiomycota) from southern China based on evidence from morphology and DNA sequence data

Two new species of Coltricia, C. austrosinensis and C. minima, are described from southern China on the basis of morphological characters and molecular evidence. Phylogenetic analysis based on the internal transcribed spacer (ITS) regions and nuclear large subunit (nLSU) ribosomal RNA gene regions indicated that the two new species were nested within the Coltricia clade in Hymenochaetales. Coltricia austrosinensis is characterized by centrally stipitate basidiocarps, lobed pileal margin, distinctly swollen stipe tip, cinnamon pore surface, large pores (1–3 per mm), and broadly ellipsoid basidiospores measuring 8–10?×?5.5–6.5 μm, with a distribution to date in subtropical China. Coltricia minima is characterized by tiny, centrally stipitate basidiocarps, entire pileal margin, uniform stipe, pileus bearing distinct concentric zones and pore surface dark greyish blue when fresh, small pores (3–4 per mm), narrow tramal hyphae (3.5–4 μm), and broadly ellipsoid to subglobose basidiospores measuring 6–7?×?4–5 μm, and occur in mixed tropical forests.     

Microcultivation of anaerobic bacteria single cells entrapped in alginate microbeads

Alginate microbeads, produced by emulsion/internal gelation, were studied for the entrapment and microcultivation of microbial cells with biotechnological potential. An anaerobic consortium which was selected for its capacity to degrade complex carbohydrates, and a pure culture of cellulose degrading bacteria were used for entrapment studies. Optimization of conditions for the formation of spherical alginate microbeads in sizes between 20 and 80 μm were examined. The best conditions were achieved by combining rapeseed methyl ester as oil phase and stirring at 100 rpm using a rotation impeller. Calcium alginate microbeads produced under these conditions were shown to present morphological stability, with large pores in the internal matrix that favours microcolony development. Finally, single cells were observed inside the beads after the entrapment procedure and microcolony formation was confirmed after cultivation in cellobiose.     

Understanding the effect of mean pore size on cell activity in collagen-glycosaminoglycan scaffolds

Mean pore size is an essential aspect of scaffolds for tissue-engineering. If pores are too small cells cannot migrate in towards the center of the construct limiting the diffusion of nutrients and removal of waste products. Conversely, if pores are too large there is a decrease in specific surface area available limiting cell attachment. However the relationship between scaffold pore size and cell activity is poorly understood and as a result there are conflicting reports within the literature on the optimal pore size required for successful tissue-engineering. Previous studies in bone tissue-engineering have indicated a range of mean pore sizes (96–150 µm) to facilitate optimal attachment. Other studies have shown a need for large pores (300–800 µm) for successful bone growth in scaffolds. These conflicting results indicate that a balance must be established between obtaining optimal cell attachment and facilitating bone growth. In this commentary we discuss our recent investigations into the effect of mean pore size in collagen-glycosaminoglycan (CG) scaffolds with pore sizes ranging from 85–325 μm and how it has provided an insight into the divergence within the literature.     

The comparative pollen morphology of genera Matricaria L. and Tripleurospemum Sch. Bip. (Asteraceae) in Turkey

Pollen morphology of four Matricaria species and 28 Tripleurospermum species was investigated with light microscopies (LM) and scanning electron microscopies (SEM). Pollen slides were prepared using Wodehouse technique. Measurements were based on 20 or more pollen grains per specimen. For SEM studies, dried pollen grains were transferred on aluminum stubs and coated with gold for 4 min in a sputter-coater. The pollen grains of Matricaria and Tripleurospermum are radially symmetric and isopolar. The pollen grains of the Matricaria are oblate-spheroidal with the polar axes 16.6–31.2 μm and the equatorial axes 18.7–23.9 μm. Tripleurospermum is oblate-spheroidal, suboblate and prolate-spheroidal with the polar axes 15.6–32.2 μm and the equatorial axes 17.7-38.5 μm. The pollen grains of Tripleurospermum are operculate and tricolporate. Matricaria is operculate and usually tricolporate or rarely syncolporate, tricolpate and tetracolporate. The pollen grain of both taxa shows echinate ornamentation. The spines are commonly conical with a broadened base and a tapered apical portion. The spine length varies between 1.8–4 μm in Tripleurospermum and 2.3–3.3 μm in Matricaria. The width of spines varies between 2.8–4.6 μm in Tripleurospermum and 2.4–3.6 μm in Matricaria. Inter-spinal area shows granulate–perforate, reticulate–perforate, rugulate–perforate ornamentations and the tectum surrounding the spine base is micro perforate. Overall exine thickness ranges from 2.8 to 4.8 μm in Tripleurospermum, 3.6 to 5.2 μm in Matricaria. Intine is thicker under pores in Tripleurospermum (0.3–0.62 μm) than in Matricaria (0.6–0.8 μm). Inter-spinal ornamentations, pollen shape and the numbers of perforations at the spin base have been observed as important morphological characters.     

Extent and Mode of Action of Cationic Legume Proteins against Listeria monocytogenes and Salmonella Enteritidis

The methylated soybean protein and methylated chickpea protein (MSP and MCP) with isoelectric points around pI 8 were prepared by esterifying 83 % of their free carboxyl groups and tested for their interactions with Listeria monocytogenes and Salmonella Enteritidis. The two substances exhibited a concentration-dependent inhibitory action against the two studied bacteria with a minimum inhibitory concentration of about 100 μg/mL. The IC_50 % of the two proteins against L. monocytogenes (17 μg/mL) was comparable to penicillin but comparatively much lower (15 μg/mL) than that of penicillin (85 μg/mL) against S. Enteritidis. The two proteins could inhibit the growth of L. monocytogenes and S. Enteritidis by about 97 and 91 %, respectively, after 6–12 h of incubation at 37 °C. The constituting subunits of MSP (methylated 11S and methylated 7S) were both responsible for its antimicrobial action. Transmission electron microscopy of the protein-treated bacteria showed various signs of cellular deformation. The cationic proteins can electrostatically and hydrophobically interact with cell wall and cell membrane, producing large pores, pore channels and cell wall and cell membrane disintegration, engendering higher cell permeability leading finally to cell emptiness, lysis and death.     

Choice of Pore Size Can Introduce Artefacts when Filtering Picoeukaryotes for Molecular Biodiversity Studies

Published results of studies based on samples size fractionated by sequential filtration (e.g. 0.2–3 μm) indicate that many ciliate, dinoflagellate and rhizarian phylotypes are found among marine picoeukaryotes. This is somewhat surprising as these protists are typically known as being large organisms (often >10 μm) and no picoplanktonic species have so far been identified. Here, the abundances of ciliate and dinoflagellate phylotypes in published molecular studies of picoeukaryotes are shown to correlate negatively with the pore size chosen for the end filter in the sequential filtrations (i.e. the filter used to collect the microbial biomass). This suggests that extracellular DNA adhering to small particles may be the source of ciliate and dinoflagellate phylotypes in picoplanktonic size fractions. This hypothesis was confirmed using real-time qPCR, which revealed significantly less dinoflagellate 18S rDNA in a 0.8–3-μm size fraction compared to 0.2–3 μm. On average, the abundance of putative extracellular phylotypes decreased by 84–89 % when a 0.8-?μm end filter was used rather than a 0.2-μm end filter. A 0.8-μm filter is, however, not sufficient to retain all picoeukaryotic cells. Thus, selection of filter pore size involves a trade-off between avoiding artefacts generated by extracellular DNA and sampling the entire picoeukaryotic community. In contrast to ciliate and dinoflagellate phylotypes, rhizarian phylotypes in the picoplankton size range do not display a pattern consistent with an extracellular origin. This is likely due to the documented existence of picoplanktonic swarmer cells within this group.     

Marrow-derived stem cell motility in 3D synthetic scaffold is governed by geometry along with adhesivity and stiffness

Design of 3D scaffolds that can facilitate proper survival, proliferation, and differentiation of progenitor cells is a challenge for clinical applications involving large connective tissue defects. Cell migration within such scaffolds is a critical process governing tissue integration. Here, we examine effects of scaffold pore diameter, in concert with matrix stiffness and adhesivity, as independently tunable parameters that govern marrow‐derived stem cell motility. We adopted an “inverse opal” processing technique to create synthetic scaffolds by crosslinking poly(ethylene glycol) at different densities (controlling matrix elastic moduli or stiffness) and small doses of a heterobifunctional monomer (controlling matrix adhesivity) around templating beads of different radii. As pore diameter was varied from 7 to 17 µm (i.e., from significantly smaller than the spherical cell diameter to approximately cell diameter), it displayed a profound effect on migration of these stem cells—including the degree to which motility was sensitive to changes in matrix stiffness and adhesivity. Surprisingly, the highest probability for substantive cell movement through pores was observed for an intermediate pore diameter, rather than the largest pore diameter, which exceeded cell diameter. The relationships between migration speed, displacement, and total path length were found to depend strongly on pore diameter. We attribute this dependence to convolution of pore diameter and void chamber diameter, yielding different geometric environments experienced by the cells within. Bioeng. 2011; 108:1181–1193. © 2010 Wiley Periodicals, Inc.     

Interference of tooth differentiation with interposed filters

The effect of interposed Nuclepore filters on the epithelio-mesenchymal interaction in embryonic mouse tooth was studied. Filters with pore sizes of 0.6 and 0.2 μm allowed differentiation of odontoblasts and ameloblasts in the bell-stage tooth germ. This differentiation progressed more rapidly when the 0.6-μm pore size filter was used. Nuclepore filters with 0.1-μm pores prevented differentiation. Electron microscopic examination revealed penetration of cell processes into the filter pores. Cytoplasmic material could be seen in the 0.6-μm pore-size filter within 3 days of cultivation, whereas, in the 0.2-μm filter pores, penetration was slight. After 6 days of cultivation, cytoplasmic material was found at all levels of the 0.2-μm pore-size filter, but not in the channels of the 0.1-μm pore-size filters, preventing differentiation. It is concluded that the 0.1-μm pore-size filter blocks tooth development at the level of mesenchymal cell differentiation into odontoblasts. It is suggested that this differentiation requires a close association between the interacting mesenchymal and epithelial cells.     

Multi-locus phylogeny and morphology reveal five new species of <Emphasis Type="Italic">Fomitiporia</Emphasis> (Hymenochaetaceae) from China

Five newly identified species of Fomitiporia (F. alpina, F. gaoligongensis, F. hainaniana, F. subrobusta and F. subtropica) and their morphological and molecular characterisation are described in this paper. Fomitiporia alpina sp. nov. is distinguished by its pileate basidiomata, parallel tramal hyphae and large basidiospores (6.5–8 × 6–8 μm), and by its gymnosperm wood-living habitat. Fomitiporia gaoligongensis sp. nov. is distinct from other species due to its semicircular pileus and subglobose to globose basidiospores (6.5–7.6 × 6–7.4 μm). Fomitiporia hainaniana sp. nov. is marked by its resupinate basidiomata, the presence of setae and small globose basidiospores (4–5 × 3.8–4.4 μm). Fomitiporia subrobusta sp. nov. is characterised by its triquetrous basidiomata, small pores (6–9 per mm) with entire and thick dissepiments, and subglobose to obovoid basidiospores (6.2–6.8 × 5.2–6 μm). Fomitiporia subtropica sp. nov. can be differentiated by its resupinate basidiomata, smaller pores (6–10 per mm) and smaller basidiospores (5.2–6 × 4.4–5 μm). Phylogenetic analysis, based on multi-gene comparison of the internal transcribed spacer regions (ITS), nuclear large subunit ribosomal RNA gene regions (nLSU), the translation elongation factor 1-α gene (tef1α) and the second subunit of RNA polymerase II (rpb2), confirmed affinity with the Fomitiporia species and showed association with similar fungi in the genus.     

Evolution of larval size in cyclostome bryozoans

Cyclostomes are the only order of stenolaemate bryozoans living today. The non-feeding larvae of modern cyclostomes metamorphose on settlement to produce a calcified dome-shaped protoecium. Protoecial diameter provides a proxy for larval size. The sparse data available on living cyclostomes suggests that protoecial diameter is about one-and-a-half times greater than larval width. Here we use protoecial diameter to estimate larval sizes in fossil and Recent cyclostome species. A total of 233 protoecia were measured, 143 from Recent cyclostomes and 90 from fossil cyclostomes, of which 84 came from the Jurassic. Protoecial diameter ranged from 82.5 to 690 μm, with 89% of protoecia having diameters between 100 and 300 μm. A comparison of 30 Jurassic with 51 Recent taxa of tubuliporine cyclostomes showed a significant difference in size frequency. Although the Recent taxa have a larger size range (83–465 μm) than the Jurassic taxa (125–249 μm), Recent species have a lower mode (125–150 μm) than the Jurassic species (175–200 μm). Most Jurassic cyclostomes may therefore have had larger larvae than their extant relatives. Reduction in larval size may be a component of the previously hypothesized reduction in overall body size resulting from competitive displacement by cheilostome bryozoans.     

Biodegradation of ballast tank coating investigated by impedance spectroscopy and microscopy

This research paper addresses the biodegradation process for ballast tank coatings in marine environments. As part of this new approach, a commercially available ballast tank coating was exposed to bacteria obtained from a culture collection and to a natural bacterial community isolated from a real ballast tank. The natural community was chosen to explore the interaction of natural biofilms with the coating, an aspect, which is not covered in standard procedures. It is shown that biological activity significantly affects the coating properties. Micro-cracks and holes have been identified using AFM. Acidic bacteria generated holes with 0.2–0.9 μm in depth and 4–9 μm in width. Whereas the natural community additionally caused cracks of 2–8 μm in depth and 1 μm in length. The overall effect of this degradation was examined using the EIS technique. However, the bacterial affected coatings (exposed to acid producing bacteria and a natural community) show a decrease in corrosion resistance. Impedance IZI values decreased over time from 1.18 × 10⁹ to 1.87 × 10⁷ Ω for acidic bacteria and from 1.71 × 10⁹ to 2.24 × 10⁷ Ω for the natural community, indicating a clear loss in coating resistance over time. It is also revealed that the coating corrosion resistance declines after 40 days of exposure for the natural community, leading to the formation of blisters. Bacterial settling could be linked to some specific biofilm patterns affecting different types of coating attack. It can be concluded that it is necessary to include natural communities in coating degradation studies to identify possible degradation mechanisms and the severity of the attack over time.     

Two new Fomitopsis species from southern China based on morphological and molecular characters

Fomitopsis cana sp. nov. and F. subtropica sp. nov. are described from southern China based on morphological and molecular characters. Both species have annual, effused-reflexed basidiomata with several small imbricate pilei protruding from a large resupinate part. F. cana is characterized by its mouse-grey to dark grey basidiomata, pores 5–8 per mm, and small cylindrical to oblong-ellipsoid basidiospores (5–6.2?×?2.1–3 μm). F. subtropica is characterized by its white, cream, straw-yellow to more or less flesh-pink basidiomata which was easily separable from the substrate, smaller pores (6–9 per mm) and smaller basidiospores (3.2–4?×?1.8–2.1 μm), and presence of yellowish oil-like substances in trama. Phylogenetic analysis based on combined ITS and nLSU sequences suggest that the two new species belong in the Fomitopsis sensu stricto group within the Antrodia clade.     

Micronization of a Soft Material: Air-Jet and Micro-Ball Milling

The air-jet and ball-mill are frequently used in fine micronization of active pharmaceutical ingredients to the order of 1–5 μm, which is important for increasing dissolution rates, and also for pulmonary delivery. In this study, we investigated the ability of air-jet and ball-mill to achieve adequate micronization on the lab scale using a model soft material, Pluronic® F-68. Material mechanical properties were characterized using the nanometer 600. Pluronic® F-68 was ball-milled in a micro-mill at different material weights and durations in liquid nitrogen vapor. In comparison, a lab scale air-jet mill was used at various milling parameters according to a full factorial design, where the response factors were particle yield and particle size distribution, which was analyzed using laser diffraction and scanning electron microscopy. The yield achieved with the micro-ball mill was 100% but was ~80% for the air-jet mill, which reduced the size of Pluronic® F-68 from 70 μm to sizes ranging between 23–39 μm median diameters. Ball milling produced particles less than 10 μm after 15 min. Although air-jet milling proved capable of particle size reduction of the relatively soft material Pluronic® F-68, limitations to the lower size range achievable were observed. The feed rate of the material into the air jet mill was a significant factor and slower feed rates lead to smaller sizes by allowing more time for particle collisions and subsequent particle breakage to occur. Micro-ball milling under cold condition was more successful at achieving a lower range particle size reduction of soft materials.     

Curcumin inhibits the metastasis of K1 papillary thyroid cancer cells via modulating E-cadherin and matrix metalloproteinase-9 expression

The anti-metastatic effect of curcumin on papillary thyroid cancer K1 cells and its underlying mechanisms were investigated. Curcumin at 12.5, 25 and 50 μM promoted mesenchymal–epithelial transition and decreased the migration rate of K1 cells by 24–87 %. Its mechanism may involve the up-regulation of E-cadherin expression levels and down-regulation of the activity and expression of matrix metalloproteinase-9.     

The influence of porosity on the hemocompatibility of polyhedral oligomeric silsesquioxane poly (caprolactone-urea) urethane

BackgroundThe physio-chemical properties of blood contacting biomaterials play an important role in determining their hemocompatibility. It is shown in literature that surface roughness and porosity have significant effect on hemocompatibility. In this study, we use a biocompatible, low thrombogenic nanocomposite polymer called POSS-PCU to test this hypothesis: would porosity compromise the hemocompatibility of POSS-PCU. We compared the hemocompatibility of POSS-PCU films of various pore sizes with PTFE, which is a commercially available material used in most blood contacting devices.MethodsSterilized POSS-PCU films with different size pores were prepared as samples and porous PTFE film were selected as control. And all samples were subjected to SEM for topograpgy, mechanical test for characterization and hemocompatibility tests to evaluate contact activation, platelet adhesion and activation, as well as whole blood clotting response to the samples.ResultsWCA significantly increased with the pore size of POSS-PCU film, whereas both tensile stress and strain decreased significantly as the sizes of pores increased. However, when compared to PTFE film with same size pores, POSS-PCU films showed both higher tensile stress and strain. Pore size had little impact over POSS-PCU's surface chemistry groups as tested by FTIR analysis. Contact activation and platelet adhesion essay also showed no significant difference between different POSS-PCU samples. However, in whole blood reactions, POSS-PCU with pores size around 2–5 μm showed higher BCI than plain films and those with pores size around 35–45 μm. POSS-PCU showed lower thrombogencity and higher hemocompatibility comparing with porous PTFE on the aspects of platelet activation, adhesion and whole blood reaction.Summary and conclusionsPOSS-PCU polymer films as a biomaterial in chronic blood contacting implants show significant lower thrombogencity and higher hemocompatibility than porous PTFE film. It is desirable as a coating or covering material in small diameter stents for treating cardiovascular diseases, cerebral vascular diseases and peripheral arterial diseases.     

Observations pertaining to the origin and ecology of microorganisms recovered from the deep subsurface of Taylorsville Basin,Virginia

To understand the conditions under which microorganisms exist in deep hydrocarbon reservoirs, sidewall cores were collected from a natural gas‐bearing formation, 2800 m below the surface in Taylorsville Basin, Virginia. Data from chemical and microbial tracers and controls indicate that the interiors of some sidewall cores contained microorganisms indigenous to the rock formation. The cultured microorganisms were composed primarily of saline‐tolerant, thermophilic fermenting, Fe(III)‐reducing, and sulfate‐reducing bacteria (1 to 10⁴ cells/g). The physiological capabilities of the cultured microorganisms are compatible with the temperature (76°C), pressure (32 MPa), and salinity (≈0.8 wt.% NaCl equivalent) in the sampled interval. The petrological data indicated that the strata contain intercrystalline pores of micrometer size, that occur between late diagenetic cement in siltstone and within cross‐cutting, mineralized fractures in shale. These pores made up only 0.04% of the rock volume, were mostly gas‐filled, and were interconnected by pore throats with diameters <0.04 μm. Because the pore throats are smaller than known bacteria, the cultured microorganisms were probably trapped within the larger pores containing alkaline, brackish, formation water. The total phospholipid fatty acid concentration of the rock samples yielded a cellular concentration equivalent to 4 x 10⁵ cells/g, much greater than had been determined by enumeration of the cultured bacteria. This may have resulted from either inhibition of dephosphorolation reactions within pores filled with reduced gases, such as methane, or the inability to culture >0.1% of the viable bacteria. The recovery of living bacteria from such an austere environment represents one of the most remarkable examples of microbial survival yet reported.     

Uptake of dissolved organic nitrogen by size-fractionated plankton along a salinity gradient from the North Sea to the Baltic Sea

The Baltic Sea is known for its ecological problems due to eutrophication caused by high nutrient input via nitrogen fixation and rivers, which deliver up to 70% of nitrogen in the form of dissolved organic nitrogen (DON) compounds. We therefore measured organic nitrogen uptake rates using self produced ¹⁵N labeled allochthonous (derived from Brassica napus and Phragmites sp.) and autochthonous (derived from Skeletonema costatum) DON at twelve stations along a salinity gradient (34 to 2) from the North Sea to the Baltic Sea in August/September 2009. Both labeled DON sources were exploited by the size fractions 0.2–1.6 μm (bacteria size fraction) and >1.6 μm (phytoplankton size fraction). Higher DON uptake rates were measured in the Baltic Sea compared to the North Sea, with rates of up to 1213 nmol N l^?1 h^?1. The autochthonous DON was the dominant nitrogen form used by the phytoplankton size fraction, whereas the heterotrophic bacteria size fraction preferred the allochthonous DON. We detected a moderate shift from >1.6 μm plankton dominated DON uptake in the North Sea and central Baltic Sea towards a 0.2–1.6 μm dominated DON uptake in the Bothnian Bay and a weak positive relationship between DON concentrations and uptake. These findings indicate that DON is an important component of plankton nutrition and can fuel primary production. It may therefore also contribute substantially to eutrophication in the Baltic Sea especially when inorganic nitrogen sources are depleted.     

Variables of Microbial Response in Natural Soil Aggregates for Soil Characterization in Different Fluvial Land Shapes

The main objective of this study was to determine changes in microbial response in natural soil aggregates for soil characterization in different fluvial land shapes. This study was carried out in fluvial lands formed on accumulated sediment depositions carried by K?z?l?rmak River. The majority soils of the study area were classified as Typic Ustifluvent and Typic Haplustept in Soil Taxonomy. It was found that macroaggregates (especially >6300 μm and 2000–4750 μm diameters) of all soil samples were higher than microaggregate of soils. In addition, it was determined that the C_org content varies between 0.41–0.91% in soil samples. C_mic content was also found higher level in aggregates involved <250 and 250–425 μm diameters as compared to other aggregate size classes. Moreover, we detected that C_org:C_mic ratio was much higher in macroaggregates than in microaggregate fractions. BR levels were also greater in macroaggregates of >6,300, 4,750–6,300 and 2,000–4,750 μm than in the other macroaggregates sizes and microaggregates. Consequently, macroaggregates have relatively more C_org level than the C_org level in microaggregates, even if the absolute values of C_mic were the lower. This study thus evidenced contrasting microbial habitats and their response in different soil aggregate size formed in various developed soils.     

Characterisation of the Poly-(Vinylpyrrolidone)-Poly-(Vinylacetate-Co-Crotonic Acid) (PVP:PVAc-CA) Interpolymer Complex Matrix Microparticles Encapsulating a Bifidobacterium lactis Bb12 Probiotic Strain

The method of producing poly-(vinylpyrrolidone)-poly-(vinylacetate-co-crotonic acid) (PVP:PVAc-CA) interpolymer complex matrix microparticles in supercritical carbon dioxide (scCO₂), encapsulating bacteria, has recently been developed. This study was aimed at probing the external and internal structure of these microparticles, which can be used in food. The encapsulation efficiency and distribution of encapsulated Bifidobacterium lactis Bb12 within these microparticles were also investigated. Scanning electron microscopy (SEM) revealed irregular, mostly small, smooth microparticles with no visible bacterial cells on the surface. However, some of the microparticles appeared to have porous surfaces. The results of a Microtrac S3500 particle size analyzer showed that the PVP:PVAc-CA interpolymer complex matrix microparticles encapsulating B. lactis Bb12 had an average particle size of 166.1 μm (<350 μm designated standard size for microparticles). The D ₁₀, D ₅₀ and D ₉₀ values for these microparticles were 48.16, 166.06 and 382.55 μm, respectively. Both SEM and confocal laser scanning microscopy showed a high density of bacterial cells within the microparticles. An average encapsulation efficiency of 96% was achieved. Consequently, the microparticles have the potential to be evenly distributed in foods, deliver adequate amounts of probiotics and produce minimal adverse effects on the texture and mouth feel of the foods into which they are incorporated.