Maximum Growth Temperature Research Articles

Growth and survival of Bacillus cereus from spores in cooked rice – One-step dynamic analysis and predictive modeling

Bacillus cereus is a spore-forming foodborne pathogen that can produce toxins causing emetic or diarrheal intoxication. Food poisoning caused by B. cereus is a significant public health concern as it is frequently associated with the consumption of starch-based food products, which are a staple food worldwide. The objective of this study was to investigate the growth and survival of B. cereus in cooked rice under changing temperatures between 1 and 48 °C. A one-step dynamic analysis was used to directly construct a tertiary model to describe the growth and survival of B. cereus and estimate the kinetic parameters.The results of one-step dynamic analysis showed that the minimum, optimum, and maximum growth temperatures were 8.2, 37.6, and 46.8 °C, respectively, with an optimal specific growth rate of 2.21 ln CFU/g/h or 0.96 log CFU/g/h. These parameters agreed well with the reported typical growth kinetics of this microorganism. In addition, this study found that the populations of B. cereus decreased gradually at the rate of 1.21 × 10−3 ln CFU/g/h per °C or 1.2 × 10−3 log CFU/g/h per °C below the minimum growth temperature.The tertiary model was validated using three dynamic growth and survival curves. The results showed that the root-mean-square-error of the predictions was 0.5 log CFU/g, suggesting that the model is reasonably accurate in predicting the growth of B. cereus in cooked rice. The results of this study can be used to predict the growth and survival of B. cereus and assess its risk in cooked rice or other starch-based products exposed to a relatively wide temperature range during manufacturing and distribution.

Temperature-dependent expression of different guanine-plus-cytosine content 16S rRNA genes in Haloarcula strains of the class Halobacteria

Haloarcula strains, which are halophilic archaea, harbour two to three copies of 16S rRNA genes (rrsA, rrsB and rrsC) in their genomes. While rrsB and rrsC (rrsBC) show almost identical sequences, rrsA shows 4–6% sequence difference and 1–3% guanine-plus-cytosine content (PGC) difference compared to rrsBC. Based on the strong correlation between the PGC of 16S rRNA genes and the growth temperatures of the prokaryotes, we hypothesised that high-PGCrrsA and low-PGCrrsBC are expressed at high and low temperatures, respectively. To verify the hypothesis, we performed sequence analyses and expression surveys of each 16S rRNA gene in eight Haloarcula strains. The secondary structure prediction of the 16S rRNA via computer simulation showed that the structural stability of 16S rRNAs transcribed from rrsA was higher than that of 16S rRNAs transcribed from rrsBC. We measured expression levels of rrsA and rrsBC under various temperature conditions by reverse-transcriptase quantitative PCR. The expression ratio of high-PGCrrsA to low-PGCrrsBC increased with cultivation temperatures in seven of eight Haloarcula strains. Our results suggest that the transcription of high-PGCrrsA and low-PGCrrsBC may be regulated in response to environmental temperature, and that 16S rRNAs transcribed from high-PGCrrsA function under high temperature conditions close to the maximum growth temperature.

Novel haloarchaeon Natrinema thermophila having the highest growth temperature among haloarchaea with a large genome size

Environmental temperature is one of the most important factors for the growth and survival of microorganisms. Here we describe a novel extremely halophilic archaeon (haloarchaea) designated as strain CBA1119T isolated from solar salt. Strain CBA1119T had the highest maximum and optimal growth temperatures (66 °C and 55 °C, respectively) and one of the largest genome sizes among haloarchaea (5.1 Mb). It also had the largest number of strain-specific pan-genome orthologous groups and unique pathways among members of the genus Natrinema in the class Halobacteria. A dendrogram based on the presence/absence of genes and a phylogenetic tree constructed based on OrthoANI values highlighted the particularities of strain CBA1119T as compared to other Natrinema species and other haloarchaea members. The large genome of strain CBA1119T may provide information on genes that confer tolerance to extreme environmental conditions, which may lead to the discovery of other thermophilic strains with potential applications in industrial biotechnology.

Maximum temperature for growth and reproduction is similar in two soil isolates of Gaertneriomyces semiglobifer (Spizellomycetales, Chytridiomycetes) from different soil environments in north eastern New South Wales, Australia

Maximum temperature for growth and reproduction is similar in two soil isolates of Gaertneriomyces semiglobifer (Spizellomycetales, Chytridiomycetes) from different soil environments in north eastern New South Wales, Australia

N-type dopants in (001) β-Ga2O3 grown on (001) β-Ga2O3 substrates by plasma-assisted molecular beam epitaxy

Ge and Sn as n-type dopants in (001) β-Ga2O3 films were investigated using plasma-assisted molecular beam epitaxy. The Ge concentration showed a strong dependence on the growth temperature, whereas the Sn concentration remains independent of the growth temperature. The maximum growth temperature at which a wide range of Ge concentrations (from 1017 to 1020 cm−3) could be achieved was 675 °C while the same range of Sn concentration could be achieved at growth temperature of 750 °C. Atomic force microscopy results revealed that higher growth temperature shows better surface morphology. Therefore, our study reveals a tradeoff between higher Ge doping concentration and high quality surface morphology on (001) β-Ga2O3 films grown by plasma-assisted molecular beam epitaxy. The Ge doped films had an electron mobility of 26.3 cm2 V−1 s−1 at the electron concentration of 6.7 × 1017 cm−3 whereas the Sn doped films had an electron mobility of 25.3 cm2 V−1 s−1 at the electron concentration of 1.1 × 1018 cm−3.

Ontogenetic habitat shift of age-0 Japanese flounder Paralichthys olivaceus on the Pacific coast of northeastern Japan: differences in timing of the shift among areas and potential effects on recruitment success

Ontogenetic habitat shift and feeding habits in the shallow (< 15 m) and deep (30–80 m) habitats of age-0 Japanese flounder Paralichthys olivaceus in Sendai Bay, the Pacific coast of northeastern Japan, were examined to understand the mechanisms that potentially enable area-specific high recruitment success. The flounder was able to use the shallow nursery habitat for about 1 year, until the next summer of their settlement (June–August) when they had reached 250 mm total length (TL). In addition, age-0 flounder between 150 and 250 mm TL used both shallow and deep habitats from winter to the next summer of their settlement, where species, size, and availability of potential food and susceptibility to predators are considerably different. These area-specific characteristics in Sendai Bay are clearly different from other areas around Japan that have been described in the literature: shorter residence in the shallow habitat and smaller size at emigration to the deep habitat. The characteristics in Sendai Bay seem to be enabled by prolonged good feeding conditions in the shallow habitat, which result from an abundant food supply and relatively lower temperature that does not exceed the uppermost temperature (25 °C) for maximum growth of the age-0 flounder. We consider that the prolonged better feeding conditions in the shallow habitat in the study area for ca. 1 year after settlement contribute to higher recruitment success.

Growth of non-toxigenic Clostridium botulinum mutant LNT01 in cooked beef: One-step kinetic analysis and comparison with C. sporogenes and C. perfringens

The objective of this study was to investigate the growth kinetics of Clostridium botulinum LNT01, a non-toxigenic mutant of C. botulinum 62A, in cooked ground beef. The spores of C. botulinum LNT01 were inoculated to ground beef and incubated anaerobically under different temperature conditions to observe growth and develop growth curves. A one-step kinetic analysis method was used to analyze the growth curves simultaneously to minimize the global residual error. The data analysis was performed using the USDA IPMP-Global Fit, with the Huang model as the primary model and the cardinal parameters model as the secondary model.The results of data analysis showed that the minimum, optimum, and maximum growth temperatures of this mutant are 11.5, 36.4, and 44.3 °C, and the estimated optimum specific growth rate is 0.633 ln CFU/g per h, or 0.275 log CFU/g per h. The maximum cell density is 7.84 log CFU/g. The models and kinetic parameters were validated using additional isothermal and dynamic growth curves. The resulting residual errors of validation followed a Laplace distribution, with about 60% of the residual errors within ±0.5 log CFU/g of experimental observations, suggesting that the models could predict the growth of C. botulinum LNT01 in ground beef with reasonable accuracy.Comparing with C. perfringens, C. botulinum LNT01 grows at much slower rates and with much longer lag times. Its growth kinetics is also very similar to C. sporogenes in ground beef. The results of computer simulation using kinetic models showed that, while prolific growth of C. perfringens may occur in ground beef during cooling, no growth of C. botulinum LNT01 or C. sporogenes would occur under the same cooling conditions. The models developed in this study may be used for prediction of the growth and risk assessments of proteolytic C. botulinum in cooked meats.

Phytoplankton bloom dynamics in turbid, well-mixed estuaries: A model study

To gain insight into mechanisms underlying phytoplankton bloom dynamics in turbid, well-mixed estuaries, experiments were conducted with an exploratory model that couples physical and biological processes. The motivation for choosing exploratory models is that they allow investigation of individual processes in isolation, therefore yielding fundamental insight into the mechanisms of the system. The Ems estuary (between the Netherlands and Germany) was selected as the prototype estuary, in which a zone of high turbidity is observed in the middle and upper reach. Results show that the model is capable of capturing the main features of the observed phytoplankton population density (P) patterns, that is, in the lower reach a spring bloom occurs, followed by a secondary bloom in autumn. Results of sensitivity studies reveal that the along-estuary distribution of suspended particulate matter (SPM) is a determining factor for the along-estuary location of blooms and it largely affects the intensity of blooms. The along-estuary advection of nutrients by the subtidal current is important for obtaining blooms with high intensities. In this model, the seasonally varying water temperature has a larger impact on the timing of spring blooms than the seasonally varying incident light intensity. The occurrence of an autumn bloom is due to the fact that during the summer season, the net specific growth rate of phytoplankton decreases. The latter is likely to result from an optimum water temperature (smaller than the maximum water temperature) for phytoplankton growth. Nevertheless, the occurrence and characteristics of autumn blooms are also influenced by seasonal variations in other aspects, for instance, loss of phytoplankton due to grazing.

Growth of Yersinia pseudotuberculosis Strains at Different Temperatures, pH Values, and NaCl and Ethanol Concentrations

Maximum growth temperature and growth limits in Luria-Bertani broth at different pH values and NaCl and ethanol concentrations were determined for 49 Yersinia pseudotuberculosis strains representing serotypes O:1, O:2, O:3, O:4, and O:5. In addition, the ability of the strains to grow at 0°C and the growth parameters at 1°C were determined. The maximum growth temperatures measured by Gradiplate temperature incubator varied between 42.2 and 43.7°C. All strains were able to grow at 0°C in Luria-Bertani broth within 17 days of incubation. At 1°C, differences were observed among strains in the maximum growth rates and area under the curve values based on optical density data, which suggests that some Y. pseudotuberculosis strains adapt faster to colder conditions. The mean maximum growth rates and area under the curve values at 1°C, as well as the mean maximum growth temperatures, were statistically significantly higher among serotype O:1 strains compared with O:3 strains and among biotype 1 compared with biotype 2 strains. All strains grew at pH 4.5, whereas none of the strains were able to grow at pH 4.2. The highest pH at which growth was observed varied between 9.0 and 9.3. For 14 strains the maximum NaCl concentration at which growth was observed was 4.8%, whereas 35 of the strains were able to grow at 5.0% NaCl. None of the strains showed growth at 5.2% NaCl. All strains were able to grow at 4.5% ethanol concentration (v/v), whereas 5.0% ethanol concentration was completely inhibitory to all strains. The observed limited physiological diversity among various Y. pseudotuberculosis strains may stem from the genetic homogeneity of the species.

Rethinking Tertiary Models: Relationships between Growth Parameters of Bacillus cereus Strains.

The maximum specific growth rates of 12 strains, pair-wise belonging to six groups of Bacillus cereus sensu lato, were fitted against temperature by a reparametrized version of the model of Ratkowsky et al. (1983). This way, the interpretation of the new parameter set was similar to that of the cardinal-values-model of Rosso and Robinson (2001), both models including the minimum, optimum and maximum temperatures for growth as well as a fourth parameter scaling along the dependent variable. The modularity of the reparametrized version of the Ratkowsky model was utilized to show a so-far undetected relationship between this scaling parameter and the cardinal temperatures, which linked even distant (e.g., mesophilic and psychotropic) strains of B. cereus. We propose that the name “tertiary modeling” should be used for investigations like ours, as logically derived from the concepts of “primary” and “secondary” modeling. Such tertiary models may reveal biological relationships between kinetic parameters within a group of strains. It can also be used to create an overarching predictive model for mixed cultures, when different strains grow together but independently of each other.

Multiple new cryptic pathogenic Phytophthora species from Fagaceae forests in Austria, Italy and Portugal

During surveys of Phytophthora diversity in natural and semi-natural Fagaceae forests in Austria, Italy and Portugal, four new cryptic species were isolated from rhizosphere soil samples. Multigene phylogeny based on nuclear ITS, ß-tubulin and HSP90 and mitochondrial cox1 and NADH1 gene sequences demonstrated that two species, P. tyrrhenica and P. vulcanica spp. nov, belong to phylogenetic Clade 7a, while the other two species, P. castanetorum and P. tubulina spp. nov, clustered together with P. quercina forming a new clade, named here as Clade 12. All four new species are homothallic and have low optimum and maximum temperatures for growth and very slow growth rates at their respective optimum temperature. They differed from each other and from related species by a unique combination of morphological characters, cardinal temperatures, and growth rates. Pathogenicity of all Phytophthora species to the root system of their respective host species was demonstrated in soil infestation trials.

Phytoplankton traits from long-term oceanographic time-series

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 576:11-25 (2017) - DOI: https://doi.org/10.3354/meps12220 Phytoplankton traits from long-term oceanographic time-series Crispin M. Mutshinda1, Zoe V. Finkel2, Claire E. Widdicombe3, Andrew J. Irwin1,* 1Mathematics & Computer Science, Mount Allison University, Sackville, NB E4L 1E6, Canada 2Environmental Science, Mount Allison University, Sackville, NB E4L 1A7, Canada 3Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK *Corresponding author: airwin@mta.ca ABSTRACT: Trait values are usually extracted from laboratory studies of single phytoplankton species, which presents challenges for understanding the immense diversity of phytoplankton species and the wide range of dynamic ocean environments. Here we use a Bayesian approach and a trait-based model to extract trait values for 4 functional types and 10 diatom species from field data collected at Station L4 in the Western Channel Observatory, English Channel. We find differences in maximum net growth rate, temperature optimum and sensitivity, half-saturation constants for light and nitrogen, and density-dependent loss terms across the functional types. We find evidence of very high linear loss rates, suggesting that grazing may be even more important than commonly assumed and differences in density-dependent loss rates across functional types, indicating the presence of strong niche differentiation among functional types. Low half-saturation constants for nitrogen at the functional type level may indicate widespread mixotrophy. At the species level, we find a wide range of density-dependent effects, which may be a signal of diversity in grazing susceptibility or biotic interactions. This approach may be a way to obtain more realistic and better-constrained trait values for functional types to be used in ecosystem modeling. KEY WORDS: Phytoplankton · Time series · Traits · Growth rate · Grazing rate · English Channel Full text in pdf format Supplementary material PreviousNextCite this article as: Mutshinda CM, Finkel ZV, Widdicombe CE, Irwin AJ (2017) Phytoplankton traits from long-term oceanographic time-series. Mar Ecol Prog Ser 576:11-25. https://doi.org/10.3354/meps12220 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 576. Online publication date: August 03, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Genetic diversity of yeasts from East Ongul Island, East Antarctica and their extracellular enzymes secretion

Microbes growing at low temperatures encounter numerous growth constraints. However, fungi that inhabit polar regions can grow and decompose organic compounds at low temperatures. Research on the biodiversity and secretion ability of yeasts from East Ongul Island, and evaluation of their extracellular enzymatic activity at temperatures ranging from −3 to 20 °C, was performed and described in this study. In total, 95 yeast strains were isolated from the surface soil on East Ongul Island, East Antarctica. Based on the internal transcribed spacer (ITS) region and 26S rDNA D1/D2 domain sequence similarity, these strains were classified into 10 genera and 16 species. All strains were categorized as basidiomycetous yeasts. One representative strain was selected from each species, and its ability to grow at temperatures between −3 and 37 °C was evaluated. Strain abilities to secrete extracellular enzymes (lipase, cellulase, and protease) at temperatures ranging from −3 to 20 °C were also investigated. Based on the optimal and maximal growth temperatures, the yeasts were classified as psychrophilic or psychrotolerant. All the strains investigated in this study were able to grow at −3 °C and in vitamin-free media. Psychrophilic yeasts, such as Glaciozyma antarctica, Gl. martinii, Mrakia gelida, and Phenoliferia glacialis, did not secrete pronounced amounts of extracellular enzymes at −3 °C; in contrast, the psychrotolerant yeasts Goffeauzyma gilvescens, Holtermanniella wattica, Tausonia pullulans, and Udeniomyces puniceus secreted copious amounts of enzymes, even at subzero temperatures. These results indicated that psychrotolerant yeasts, rather than psychrophilic yeasts, play important roles in the nutrient cycle in the East Ongul Island ecosystem at near-subzero temperatures.

Taxonomic novelties in Aspergillus section Fumigati: A. tasmanicus sp. nov., induction of sexual state in A. turcosus and overview of related species

The phylogenetic position of two Aspergillus strains isolated from Australian soil and phenotypically resembling A. unilateralis was investigated by using multigene phylogeny based on β-tubulin (benA), calmodulin (CaM), actin (act), and RNA polymerase II second largest subunit (RPB2) genes. The analysis supported their placement into a separate lineage within a well-supported clade containing 10 other members of section Fumigati (“A. unilateralis clade”). Comparisons of extrolite profiles, taxonomically informative morphological and physiological characters were made, and it was discovered that the two strains can be differentiated from all relatives by their low maximum growth temperature, short stipes, and ornamentation of conidia. The data justified the proposal of a new species, A. tasmanius sp. nov. Amplification of mating-type genes showed that the A. unilateralis clade contains five heterothallic species. Only the MAT1-1-1 idiomorph was detected among isolates of A. unilateralis, A. tasmanicus, and A. marvanovae, while isolates having both opposite mating types were detected in A. turcosus and A. nishimurae. The sexual state of A. turcosus was induced by mating experiments and is described in this study. Ascospores of this species were unique by their smooth to finely verrucose convex surface and two well-visible equatorial crests. Some exometabolites detected in A. marvanovae and A. tasmanicus are also indicative of a perfect state, thus supporting the hypothesis that these species have cryptic sexual cycles. The epitype and ex-epitype culture is designated for A. nishimurae to facilitate further taxonomic work with this species.

BACTÉRIAS DIAZOTRÓFICAS NÃO SIMBIÓTICAS E ENRAIZAMENTO DE ESTACAS SEMILENHOSAS DE OLIVEIRA (&lt;i&gt;Olea europaea&lt;/i&gt; L.)

Bactérias diazotróficas não simbióticas (BDNS) atuam no desenvolvimento das plantas principalmente por meio da fixação biológica de nitrogênio e pela produção e liberação de substâncias reguladoras do crescimento vegetal. Não há descrito na literatura internacional o efeito dessas bactérias no enraizamento de estacas de oliveira, o qual tem sido proporcionado pelo uso de tratamento hormonal à base de ácido indolbutírico (AIB).Em vista disso, este trabalho objetivou avaliar a diversidade fisiológica de isolados obtidos em amostras de solo da Reserva Biológica Serra dos Toledos (Itajubá - MG) e de estirpes-tipo de BDNS, e o potencial de substituição do hormônio AIB no enraizamento de estacas semilenhosas de oliveira na Fazenda Experimental de Maria da Fé (FEMF-EPAMIG). Os isolados foram distribuídos em 5 grupos (G1 a G5) de acordo com suas características fenotípicas culturais baseadas em cor, diâmetro e consistência das colônias, e as estirpes-tipo utilizadas foram Azospirillum brasilense (BR11001), Azospirillum amazonense (BR11040), Herbaspirillum seropedicae (BR11175) e Burkholderia brasilensis (BR11340). A diversidade fisiológica foi avaliada através de experimentos de solubilização de fosfato, tolerância a diferentes condições de pH, temperatura e produção de ácido indolacético (AIA). Para avaliação do potencial de enraizamento nas estacas semilenhosas de oliveira foram utilizados os cultivares Ascolano 315, Arbequina e Grappolo 541, oriundas do banco de germoplasma da FEMF-EPAMIG. Aplicaram-se 33 tratamentos, nos quais as estacas foram inoculadas com os grupos de isolados bacterianos, com as estirpes-tipo, sem inoculação (controle) e apenas com AIB, comercialmente utilizado na FEMF-EPAMIG. Apenas dois isolados mostraram capacidade de solubilização de fosfato. Os grupos de isolados e das estirpes-tipo apresentaram exigências ambientais muito similares com amplas faixas de condições ótimas de pH (5,0 a 9,0) e temperatura (15-35ºC) para máximo crescimento. Os isolados e estirpes-tipo apresentaram uma produção de AIA variando de 110,53 a 383,58 µg mL-1, sendo que os grupos dos isolados, em geral, não diferiram significativamente dos valores obtidos pelas estirpes-tipo. Todos os grupos de isolados apresentam potencial de enraizamento de estacas de oliveira, sendo aqueles dos grupos 1 e 4 mais indicados para o cultivar Arbequina, grupo 2 para o Grappolo 541 e grupos 1 e 5 para o Ascolano 315, com desempenhos semelhantes àquele proporcionado pelo AIB.

Identification and characterization of Cr-, Cd-, and Ni-tolerant bacteria isolated from mine tailings

ABSTRACTEleven bacterial strains were isolated from soil samples collected from mine tailings. Bacterial strains were checked for tolerance against heavy metals (Cr, Cd, Ni), using the agar dilution method. All the strains showed multiple tolerances against heavy metals, but the most promising results appeared in strains BCr3, BCd33, and BNi11: they were tolerant to 15 mM of Cr6+, 7.5 mM of Cd2+, and 10 mM of Ni2+, respectively. The effect of heavy metals on bacterial growth was tested together with their ability to grow in different pH, NaCl, and temperature values. Bacterial isolates grew well between pH 7.5 and 8.5. The optimum temperature for maximum growth was between 35 and 37°C, and no significant change in bacterial growth was observed in the presence of 2% NaCl. In addition, the bioaccumulation potential of bacterial strains was investigated. Bacterial strains BCr3, BCd33, and BNi11 showed high bioaccumulation ability of Cr (68.7%), Cd (72.4%), and Ni (69.8%), respectively. All bacterial isolates were identified by 16S rRNA gene sequencing. Analysis of plasmid content revealed that all bacterial isolates contained a single plasmid. Further, polymerase chain reaction together with DNA sequence analysis was used to screen all bacterial strains for the presence metal tolerance genes (czcD, chrA, chrB, czcB, czcC, nccA, and cadA) on both plasmid and chromosomal genomes.

Soil Temperature and Maize Nitrogen Uptake Improvement Under Partial Root-Zone Drying Irrigation

Soil temperature is a major effective factor on the soil and plant biological properties. Irrigation can affect soil temperature and thereby induces a temperature effect on plant growth, which may result in an economic increase due to higher yield and plant nutrition. A field experiment was carried out to investigate the effects of three irrigation strategies including full irrigation (FI), partial root-zone drying (PRD) and deficit irrigation (DI) on soil temperature and the consequent results on the grain yield and N uptake of maize (Zea May L.). Soil temperature was measured by time domain reflectometry (TDR) sensors during the 2010 growing season. Irrigation treatments were applied from 55 to 107 d after planting. The PRD treatment caused soil temperature to be in a favorable domain for a longer period (for over 60% of the measuring dates) as a consequent result of water movement to deeper soil layers compared with the other treatments; the PRD treatment also reduced soil temperature at deeper soil depths to below the maximum favorable soil temperature for maize root growth, which resulted in deeper root penetration due to both water availability and favorable soil temperature. Compared to the FI treatment, the PRD treatment increased root water uptake by 50% and caused no significant reduction in total N uptake, while this was not observed in the DI treatment partially due to the negative temperature effect of DI on plant growth, which consequently affected the water and nutrient uptake. A longer vegetation period in the PRD treatment was observed due to higher leaf N concentrations and no significant reduction in maize grain yield occurred in the PRD treatment, compared with those in the FI treatment. Based on the results, having 15.2% water saving during the whole growing season, the PRD irrigation would positively affect soil temperature and the water and nutrient uptake as a consequent, which thereby would prevent significant reduction in maize grain yield.

Multiplication of Legionella pneumophila Sequence Types 1, 47, and 62 in Buffered Yeast Extract Broth and Biofilms Exposed to Flowing Tap Water at Temperatures of 38°C to 42°C.

Growth of Legionella pneumophila in tap water installations is a serious public health concern. The organism includes more than 2,100 varieties (sequence types). More than 50% of the reported cases of Legionnaires' disease are caused by a few sequence types which are very rarely detected in the environment. Strains of selected virulent sequence types proliferated in biofilms on surfaces exposed to warm (38°C) tap water to the same level as environmental varieties and multiplied well as pure culture in a nutrient-rich medium at temperatures of 42 and 43°C. However, these organisms did not grow in the biofilms at temperatures of ≥41°C. Typical host amoebae also did not multiply at these temperatures. Apparently, proliferation of thermotolerant host amoebae is needed to enable multiplication of the virulent L. pneumophila strains in the environment at elevated temperatures. The detection of these amoebae in water installations therefore is a scientific challenge with practical implications.

Isolation and characterization of an Antarctic Flavobacterium strain with agarase and alginate lyase activities

AbstractSeveral bacteria that are associated with macroalgae can use phycocolloids as a carbon source. Strain INACH002, isolated from decomposing Porphyra (Rhodophyta), in King George Island, Antarctica, was screened and characterized for the ability to produce agarase and alginate-lyase enzymatic activities. Our strain INACH002 was identified as a member of the genus Flavobacterium, closely related to Flavobacterium faecale, using 16S rRNA gene analysis. The INACH002 strain was characterized as psychrotrophic due to its optimal temperature (17ºC) and maximum temperature (20°C) of growth. Agarase and alginate-lyase displayed enzymatic activities within a range of 10°C to 50°C, with differences in the optimal temperature to hydrolyze agar (50°C), agarose (50°C) and alginate (30°C) during the first 30 min of activity. Strain Flavobacterium INACH002 is a promising Antarctic biotechnological resource; however, further research is required to illustrate the structural and functional bases of the enzymatic performance observed during the degradation of different substrates at different temperatures.

(Invited) Processing Technologies for Advanced Ge Devices

With proceeding CMOS device scaling, process technologies become more and more challenging as the allowable thermal budget for device processing continuously reduces. This is especially the case during epitaxial growth, where a reduction of the thermal budget is required for a number of potential reasons (e.g. to avoid uncontrolled layer relaxation of strained layers, surface reflow of narrow FIN structures, as well as doping diffusion and material intermixing). Different aspects become even more challenging when Ge is used as a high-mobility channel material and when the device concept moves from a FINFET design to a nanowire FET design (also called Gate All Around FET). In this presentation we will address some of the challenges involved with the integration of high mobility Group IV materials in these advanced device structures. Recently, we described the issue of Ge thermal instability against surface migration during selective epitaxial growth (SEG) of Ge by means of Chemical Vapor Deposition (CVD) in extremely narrow channels isolated by SiO2 [1]. Above a critical growth temperature filling of narrow channels is prohibited by Ge migration over the surface, due to the high Ge chemical potential in such narrow channels. The design of the FIN structure affects the maximal allowable growth temperature. This is critical as maintaining material quality sets a lower limit on the growth temperature [2]. Similar limitations need to be taken into account for the SEG of compressive strained Ge on top of a SiGe strain relaxed buffer (SRB). In addition, the reduced STI depth as used for high density FINs restricts the thickness of the SRB layer. The use of a V-shaped Si recess, combined with the deposition of a Ge-rich SiGe seed layer before the SRB growth, allows to reduce the Si0.3Ge0.7SRB thickness down to ~55nm while maintaining full strain relaxation (Fig. 1a). To investigate the strain state in more detail, reciprocal space maps (RSMs) were performed both along (longitudinal) and across (transverse) the fins [3,4]. From the RSMs, it is clear that the SiGe SRBs are relaxed with respect to the Si substrate. The Ge cap layer is uniaxially strained along the fins, with some relaxation occurring across the fins (Fig. 1b,c). An ultrathin Si layer is typically used to passivate the Ge surface in the high k gate module. The risk for Ge surface reflow, which in turn would lead to a (partial) relaxation of the strained Ge layer, sets the need to use high order Si-precursors such as Si3H8 and Si4H10to enable epitaxial growth at the required extremely low Si growth temperatures (< 350 °C) [4,5]. Horizontal gate all around (GAA) FETs are being considered a next logical step in scaling of Fin FETs for the 7 and 5 nm technological nodes. Their production promises little deviation from a standard Fin FETs processing flow and dramatic improvement of electro-static properties. In order to produce GAA FETs a stacking of two materials, typically Si/SiGe or SiGe/Ge, is used. An ultimate scaling of this technology assumes use of either Si or Ge and SiGe with high Ge contents close to 50%. Growth of such Si/SiGe or Ge/SiGe stacks with a large lattice mismatch is challenging since it is can only be done at low temperatures to avoid strain relaxation which would go together with defect incorporation. The use of higher order precursors allows to deposit fully strained and defect free Si/Si0.6Ge0.4 and Ge/Si 0.35 Ge 0.65 stacks with sharp interfaces between layers (Fig. 2), which are the most important requirements for GAA production. It enables us to demonstrate GAA FETs made of vertically stacked horizontal nanowires with excellent short-channel characteristics [8]. Acknowledgements: The imec core CMOS program members, European Commission, local authorities and the imec pilot line are acknowledged for their support. Epi layers are grown in EpsilonTM3200 and IntrepidTMXP systems from ASM. Air Liquide Advanced Materials is acknowledged for providing advanced precursor gases and Bruker Semiconductor Division for their kind support in XRD characterization of high mobility materials implemented in complex device architectures.