PacBio assembly of a Plasmodium knowlesi genome sequence with Hi-C correction and manual annotation of the SICAvar gene family

Plasmodium knowlesi has risen in importance as a zoonotic parasite that has been causing regular episodes of malaria throughout South East Asia. The P. knowlesi genome sequence generated in 2008 highlighted and confirmed many similarities and differences in Plasmodium species, including a global view of several multigene families, such as the large SICAvar multigene family encoding the variant antigens known as the schizont-infected cell agglutination proteins. However, repetitive DNA sequences are the bane of any genome project, and this and other Plasmodium genome projects have not been immune to the gaps, rearrangements and other pitfalls created by these genomic features. Today, long-read PacBio and chromatin conformation technologies are overcoming such obstacles. Here, based on the use of these technologies, we present a highly refined de novo P. knowlesi genome sequence of the Pk1(A+) clone. This sequence and annotation, referred to as the 'MaHPIC Pk genome sequence', includes manual annotation of the SICAvar gene family with 136 full-length members categorized as type I or II. This sequence provides a framework that will permit a better understanding of the SICAvar repertoire, selective pressures acting on this gene family and mechanisms of antigenic variation in this species and other pathogens.

Malaria diagnostics and surveillance in the post-genomic era

Genome sequences are available for 3 human-infecting malaria parasites, Plasmodium falciparum, P. vivax and P. knowlesi, and population genomics data are available for many endemic regions. This review summarizes how genomic data have been used to develop new, species-specific molecular targets for better malaria diagnosis. The combination of bioinformatics and genomics has been used to identify new sequence targets suitable for diagnostic applications and assess their viability within the context of global Plasmodium sequence variation. The selection criteria maximized the sensitivity and specificity of the novel targets. At least one target from each species was found to be suitable for molecular diagnosis of malaria with some advantages over existing molecular methods. The promise of using genome sequence data to develop sensitive, genus- or species-specific diagnostic methods for other pathogens of public health interest is strong. This undertaking together with what we envision as the future of malaria diagnosis in the 'omic' era is discussed.

Changes in nonstructural protein 3 are associated with attenuation in avian coronavirus infectious bronchitis virus

Full-length genome sequencing of pathogenic and attenuated (for chickens) avian coronavirus infectious bronchitis virus (IBV) strains of the same serotype was conducted to identify genetic differences between the pathotypes. Analysis of the consensus full-length genome for three different IBV serotypes (Ark, GA98, and Mass41) showed that passage in embryonated eggs, to attenuate the viruses for chickens, resulted in 34.75–43.66% of all the amino acid changes occurring in nsp 3 within a virus type, whereas changes in the spike glycoprotein, thought to be the most variable protein in IBV, ranged from 5.8 to 13.4% of all changes. The attenuated viruses did not cause any clinical signs of disease and had lower replication rates than the pathogenic viruses of the same serotype in chickens. However, both attenuated and pathogenic viruses of the same serotype replicated similarly in embryonated eggs, suggesting that mutations in nsp 3, which is involved in replication of the virus, might play an important role in the reduced replication observed in chickens leading to the attenuated phenotype.

Building bioinformatics capacity in West Africa

African scientists need more bioinformatics training in order to make innovative contributions to global biotechnology. To address the bioinformatics skills gap in West Africa, various training initiatives have been established in the sub-region. We present the activities of the West African Biotechnology Workshops (http://www.wabw.org/) in the past three years, and report on a symposium on bioinformatics and applied genomics in West Africa. To establish and sustain regional and national networks, stronger and increased government commitment by way of financial and infrastructural support for bioinformatics capacity building in West Africa is required.

A Multiplex-PCR approach to identification of the Brazilian intermediate hosts of Schistosoma mansoni

Due to difficulties concerning morphological identification of planorbid snails of the genus Biomphalaria, and given a high variation of characters and in the organs with muscular tissue, we designed specific polymerase chain reaction (PCR) primers for Brazilian snail hosts of Schistosoma mansoni from available sequences of internal transcribed spacer 2 (ITS2) of the ribosomal RNA gene. From the previous sequencing of the ITS2 region, one primer was designed to anchor in the 5.8S conserved region and three other species-specific primers in the 28S region, flanking the ITS2 region. These four primers were simultaneously used in the same reaction (Multiplex-PCR), under high stringency conditions. Amplification of the ITS2 region of Biomphalaria snails produced distinct profiles (between 280 and 350 bp) for B. glabrata, B. tenagophila and B. straminea. The present study demonstrates that Multiplex-PCR of ITS2-DNAr showed to be a promising auxiliary tool for the morphological identification of Biomphalaria snails, the intermediate hosts of S. mansoni.

Recent expansion of Toxoplasma through enhanced oral transmission

The global predominance of three clonal Toxoplasma gondii lineages suggests that they are endowed with an exceptional trait responsible for their current parasitism of nearly all warm-blooded vertebrates. Genetic polymorphism analyses indicate that these clonal lineages emerged within the last 10,000 years after a single genetic cross. Comparison with ancient strains (approximately 1 million years) suggests that the success of the clonal lineages resulted from the concurrent acquisition of direct oral infectivity. This key adaptation circumvented sexual recombination, simultaneously promoting transmission through successive hosts, hence leading to clonal expansion. Thus, changes in complex life cycles can occur rapidly and can profoundly influence pathogenicity.

Chloroplast transit peptide prediction: a peek inside the black box

Previous work in predicting protein localization to the chloroplast organelle in plants led to the development of an artificial neural network-based approach capable of remarkable accuracy in its prediction (ChloroP). A common criticism against such neural network models is that it is difficult to interpret the criteria that are used in making predictions. We address this concern with several new prediction methods that base predictions explicitly on the abundance of different amino acid types in the N-terminal region of the protein. Our successful prediction accuracy suggests that ChloroP uses little positional information in its decision-making; an unexpected result given the elaborate ChloroP input scheme. By removing positional information, our simpler methods allow us to identify those amino acids that are useful for successful prediction. The identification of important sequence features, such as amino acid content, is advantageous if one of the goals of localization predictors is to gain an understanding of the biological process of chloroplast localization. Our most accurate predictor combines principal component analysis and logistic regression. Web-based prediction using this method is available online at http://apicoplast.cis.upenn.edu/pclr/.

Nuclear-encoded, plastid-targeted genes suggest a single common origin for apicomplexan and dinoflagellate plastids

The phylum Apicomplexa encompasses a large number of intracellular protozoan parasites, including the causative agents of malaria (Plasmodium), toxoplasmosis (Toxoplasma), and many other human and animal diseases. Apicomplexa have recently been found to contain a relic, nonphotosynthetic plastid that has attracted considerable interest as a possible target for therapeutics. This plastid is known to have been acquired by secondary endosymbiosis, but when this occurred and from which type of alga it was acquired remain uncertain. Based on the molecular phylogeny of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes, we provide evidence that the apicomplexan plastid is homologous to plastids found in dinoflagellates-close relatives of apicomplexa that contain secondary plastids of red algal origin. Surprisingly, apicomplexan and dinoflagellate plastid-targeted GAPDH sequences were also found to be closely related to the plastid-targeted GAPDH genes of heterokonts and cryptomonads, two other groups that contain secondary plastids of red algal origin. These results address several outstanding issues: (1) apicomplexan and dinoflagellate plastids appear to be the result of a single endosymbiotic event which occurred relatively early in eukaryotic evolution, also giving rise to the plastids of heterokonts and perhaps cryptomonads; (2) apicomplexan plastids are derived from a red algal ancestor; and (3) the ancestral state of apicomplexan parasites was photosynthetic.

Phylogenetic relationships among Brazilian Biomphalaria species (Mollusca: Planorbidae) based upon analysis of ribosomal ITS2 sequences

In spite of their abundance, widespread distribution and medical importance, the phylogenetic relationships among Biomphalaria snails have received relatively little attention. We have collected and studied 29 populations of snails obtained from different localities from Brazil. We have sequenced the ribosomal DNA second internal transcribed spacer (ITS2) from the following Biomphalaria species: B. glabrata, B. tenagophila tenagophila, B. occidentalis, B. straminea, B. peregrina, B. kuhniana, B. schrammi, B. amazonica, B. oligoza, B. intermedia and an outgroup species Helisoma duryi. The sequence from each species is unique. Three different methods of phylogenetic reconstruction were used (distance, maximum parsimony and maximum likelihood). The resulting phylogenetic trees obtained by these methods basically support current systematic relationships based on morphological characters alone. This study demonstrates that the ITS2 region contains markers useful for identification and determination of relationships among Biomphalaria species.

AVP2, a sequence-divergent, K(+)-insensitive H(+)-translocating inorganic pyrophosphatase from Arabidopsis

Plant vacuolar H(+)-translocating inorganic pyrophosphatases (V-PPases; EC 3.6.1.1) have been considered to constitute a family of functionally and structurally monotonous intrinsic membrane proteins. Typified by AVP1 (V. Sarafian, Y. Kim, R.J. Poole, P.A. Rea [1992] Proc Natl Acad Sci USA 89: 1775-1779) from Arabidopsis, all characterized plant V-PPases share greater than 84% sequence identity and catalyze K(+)-stimulated H(+) translocation. Here we describe the molecular and biochemical characterization of AVP2 (accession no. AF182813), a sequence-divergent (36% identical) K(+)-insensitive, Ca(2+)-hypersensitive V-PPase active in both inorganic pyrophosphate hydrolysis and H(+) translocation. The differences between AVP2 and AVP1 provide the first indication that plant V-PPases from the same organism fall into two distinct categories. Phylogenetic analyses of these and other V-PPase sequences extend this principle by showing that AVP2, rather than being an isoform of AVP1, is but one representative of a novel category of AVP2-like (type II) V-PPases that coexist with AVP1-like (type I) V-PPases not only in plants, but also in apicomplexan protists such as the malarial parasite Plasmodium falciparum.

Transport and trafficking: Toxoplasma as a model for Plasmodium

Like Plasmodium, the protozoan parasite Toxoplasma gondii is a member of the phylum Apicomplexa, and an obligate intracellular pathogen. Unlike Plasmodium, however, Toxoplasma is highly amenable to experimental manipulation in the laboratory. The development of molecular transformation protocols for T. gondii has provided both scientific precedent and practical selectable markers for Plasmodium. Beyond the feasibility of molecular biological experimentation now possible in both systems, the high frequency of stable transformation in Toxoplasma allows this parasite to be used for molecular genetic analysis. The ability to control homologous vs. non-homologous recombination in T. gondii permits gene knockouts/allelic replacements at previously cloned loci, and saturation insertional mutagenesis of the entire parasite genome (and cloning of the tagged loci). T. gondii also exhibits unusual ultrastructural clarity, facilitating cell biological analysis. The accessibility of Toxoplasma as an experimental system allows this parasite to be used as a surrogate for asking many questions that cannot easily be addressed in Plasmodium itself. T. gondii also serves as a model system for genetic exploration of parasite biology and host-parasite interactions. Success stories include: biochemical analysis of antifolate resistance mechanisms; pharmacological studies on the mechanisms of macrolide activity; genetic identification of nucleobase/nucleoside transporters and metabolic pathways; and cell biological characterization of the apicomplexan plastid. As with any model system, not all questions of interest to malariologists can be addressed in Toxoplasma; differentiating between sensible and foolish questions requires familiarity with the biological similarities and differences of these systems.

The targets of the lytic antibody response against Trypanosoma cruzi

Trypanosoma cruzi trypomastigotes, but not epimastigotes, are normally resistant to the lytic effects of complement from vertebrate hosts susceptible to infection. This resistance facilitates parasite survival and infectivity. During the course of chronic infections, however, the vertebrate hosts produce antibodies that render the trypomastigotes sensitive to lysis, primarily via the alternative complement cascade and amplified by the classical pathway. Here, Greice Krautz, Jessica Kissinger and Antoniana Krettli summarize research on lytic antibodies, and on their respective target(s) on the T. cruzi surface. These targets are useful in tests aimed at the diagnosis of chronic Chagas disease for control of cure after specific treatment and for vaccine development.

Origin, targeting, and function of the apicomplexan plastid

The discovery of a plastid in Plasmodium, Toxoplasma and related protozoan parasites provides a satisfying resolution to several long-standing mysteries: the mechanism of action for various surprisingly effective antibiotics; the subcellular location of an enigmatic 35 kb episomal DNA; and the nature of an unusual intracellular structure containing multiple membranes. The apicomplexan plastid highlights the importance of lateral genetic transfer in evolution and provides an accessible system for the investigation of protein targeting to secondary endosymbiotic organelles. Combining molecular genetic identification of targeting signals with whole genome analysis promises to yield a complete picture of organellar metabolic pathways and new targets for drug design.

Evolutionary changes in sites and timing of actin gene expression in embryos of the direct- and indirect-developing sea urchins, Heliocidaris erythrogramma and H. tuberculata

We describe an evolutionary comparison of expression of the actin gene families of two congeneric sea urchins. Heliocidaris tuberculata develops indirectly via a planktonic feeding pluteus that forms a juvenile rudiment after a long period of larval development. H. erythrogramma is a direct developer that initiates formation of a juvenile rudiment immediately following gastrulation. The developmental expression of each actin isoform of both species was determined by in situ hybridization. The observed expression patterns are compared with known expression patterns in a related indirect-developing sea urchin, Strongylocentrotus purpuratus. Comparisons reveal unexpected patterns of conserved and divergent expression. Cytoplasmic actin, CyIII, is expressed in the aboral ectoderm cells of the indirect developers, but is an unexpressed pseudogene in H. erythrogramma, which lacks aboral ectoderm. This change is correlated with developmental mode. Two CyII actins are expressed in S. purpuratus, and one in H. erythrogramma, but no CyII is expressed in H. tuberculata despite its great developmental similarity to S. purpuratus. CyI expression differs slightly between Heliocidaris and Strongylocentrotus with more ectodermal expression in Heliocidaris. Evolutionary changes in actin gene expression reflect both evolution of developmental mode as well as a surprising flexibility in gene expression within a developmental mode.

Plasmodium inui is not closely related to other quartan Plasmodium species

Plasmodium inui (Halberstaedter and von Prowazek, 1907), a malarial parasite of Old World monkeys that occurs in isolated pockets throughout the Celebes, Indonesia, Malaysia, and the Philippines, has traditionally been considered to be related more closely to Plasmodium malariae of humans (and its primate counterpart Plasmodium brasilianum), than to other primate Plasmodium species. This inference was made in part because of the similarities in the periodicities or duration of the asexual cycle in the blood, the extended sporogonic cycle, and the longer period of time for development of the pre-erythrocytic stages in the liver. Both P. inui and P. malariae have quartan (72 hr) periodicities associated with their asexual cycle, whereas other primate malarias, such as Plasmodium fragile and Plasmodium cynomolgi, are associated with tertian periodicities (48 hr), and Plasmodiumn knowlesi, with a quotidian (24 hr) periodicity. Phylogenetic analyses of portions of orthologous small subunit ribosomal genes reveal that P. inui is actually more closely related to the Plasmodium species of the "vivax-type" lineage than to P. malariae. Ribosomal sequence analysis of many different, geographically isolated, antigenically distinct P. inui isolates reveals that the isolates are nearly identical in sequence and thus members of the same species.

Regulation and trafficking of three distinct 18 S ribosomal RNAs during development of the malaria parasite

The human malaria parasite Plasmodium vivax has been shown to regulate the transcription of two distinct 18 RNAs during development. Here we show a third and distinctive type of ribosome that is present shortly after zygote formation, a transcriptional pattern of ribosome types that relates closely to the developmental state of the parasite and a phenomenon that separates ribosomal types at a critical phase of maturation. The A-type ribosome is predominantly found in infected erythrocytes of the vertebrate and the mosquito blood meal. Transcripts from the A gene are replaced by transcripts from another locus, the O gene, shortly after fertilization and increase in number as the parasite develops on the mosquito midgut. Transcripts from another locus, the S gene, begins as the oocyst form of the parasite matures. RNA transcripts from the S gene are preferentially included in sporozoites that bud off from the oocyst and migrate to the salivary gland while the O gene transcripts are left within the oocyst. Although all three genes are typically eukaryotic in structure, the O gene transcript, described here, varies from the other two in core regions of the rRNA that are involved in mRNA decoding and translational termination. We now can correlate developmental progression of the parasite with changes in regions of rRNA sequence that are broadly conserved, where sequence alterations have been related to function in other systems and whose effects can be studied outside of Plasmodium. This should allow assessment of the role of translational control in parasite development.

Rapid evolution in a conserved gene family. Evolution of the actin gene family in the sea urchin genus Heliocidaris and related genera

Camarodont sea urchins possess a rapidly evolving actin gene family whose members are expressed in distinct cell lineages in a developmentally regulated fashion. Evolutionary changes in the actin gene family of echinoids include alterations in number of family members, site of expression, and gene linkage, and a dichotomy between rapidly and slowly evolving isoform-specific 3' untranslated regions. We present sequence comparisons and an analysis of the actin gene family in two congeneric sea urchins that develop in radically different modes, Heliocidaris erythrogramma and H. tuberculata. The sequences of several actin genes from the related species Lytechinus variegatus are also presented. We compare the features of the Heliocidaris and Lytechinus actin genes to those of the the actin gene families of other closely related sea urchins and discuss the nature of the evolutionary changes among sea urchin actins and their relationship to developmental mode.

Comparison of circumsporozoite proteins from avian and mammalian malarias: biological and phylogenetic implications

The circumsporozoite (CS) protein of malaria parasites (Plasmodium) covers the surface of sporozoites that invade hepatocytes in mammalian hosts and macrophages in avian hosts. CS genes have been characterized from many Plasmodium that infect mammals; two domains of the corresponding proteins, identified initially by their conservation (region I and region II), have been implicated in binding to hepatocytes. The CS gene from the avian parasite Plasmodium gallinaceum was characterized to compare these functional domains to those of mammalian Plasmodium and for the study of Plasmodium evolution. The P. gallinaceum protein has the characteristics of CS proteins, including a secretory signal sequence, central repeat region, regions of charged amino acids, and an anchor sequence. Comparison with CS signal sequences reveals four distinct groupings, with P. gallinaceum most closely related to the human malaria Plasmodium falciparum. The 5-amino acid sequence designated region I, which is identical in all mammalian CS and implicated in hepatocyte invasion, is different in the avian protein. The P. gallinaceum repeat region consists of 9-amino acid repeats with the consensus sequence QP(A/V)GGNGG(A/V). The conserved motif designated region II-plus, which is associated with targeting the invasion of liver cells, is also conserved in the avian protein. Phylogenetic analysis of the aligned Plasmodium CS sequences yields a tree with a topology similar to the one obtained using sequence data from the small subunit rRNA gene. The phylogeny using the CS gene supports the proposal that the human malaria P. falciparum is significantly more related to avian parasites than to other parasites infecting mammals, although the biology of sporozoite invasion is different between the avian and mammalian species.

Sea urchin Hox genes: insights into the ancestral Hox cluster

We describe the Hox cluster in the radially symmetric sea urchin and compare our findings to what is known from clusters in bilaterally symmetric animals. Several Hox genes from the direct-developing sea urchin Heliocidaris erythrogramma are described. CHEF gel analysis shows that the Hox genes are clustered on a < or = 300 kilobase (kb) fragment of DNA, and only a single cluster is present, as in lower chordates and other nonvertebrate metazoans. Phylogenetic analyses of sea urchin, amphioxus, Drosophila, and selected vertebrate Hox genes confirm that the H. erythrogramma genes, and others previously cloned from other sea urchins, belong to anterior, central, and posterior groups. Despite their radial body plan and lack of cephalization, echinoderms retain at least one of the anterior group Hox genes, an orthologue of Hox3. The structure of the echinoderm Hox cluster suggests that the ancestral deuterostome had a Hox cluster more similar to the current chordate cluster than was expected Sea urchins have at least three Abd-B type genes, suggesting that Abd-B expansion began before the radiation of deuterostomes.

Structure and evolution of CyI cytoplasmic actin-encoding genes in the indirect- and direct-developing sea urchins Heliocidaris tuberculata and Heliocidaris erythrogramma

The CyI cytoplasmic actin-encoding genes of Heliocidaris erythrogramma (He), a direct-developing sea urchin, and H. tuberculata, an indirect developer, were isolated and compared to the homologous CyI gene of another indirect developer, Strongylocentrotus purpuratus. Comparisons show that despite the differences in development, the actin gene structures and sequences are highly similar. The coding and 3' untranslated regions are conserved. The 5' He regulatory region has an inserted repeat element, but is otherwise similar to its homologues in the arrangement of presumptive transcription control elements.

Microbiology and Composition of Snack Sausages

Chemical, bacteriological and processing characteristics of experimental and commercial snack sausages were investigated. Snack sausages are narrow diameter (ca. 10-12 mm), all-beef products which are relatively dry and shelf-stable, and which may or may not be fermented. The bacterial flora of each product consisted of gram-positive, catalase-positive sporeforming rods (bacilli), reflecting a time-temperature effect of heating/smoking which destroyed most other organisms. The products have low moisture content (av. 20.6%), water activity (av. 0.78), and moisture/protein (M/P) ratio (av. 0.81/1). Judged by the sausage classification system of Acton and Dick relating moisture content to M/P ratio, the snack sausages are fully dry products. The yield of snack sausage prepared in our pilot plant was 39.6% but increased to 51.4% when the initial fat content of the meat mixture was increased from 7.2 to 25.7%.

Effects of Controlled Atmospheres on Production of Sesquiterpenoid Stress Metabolites by White Potato Tuber: Possible Involvement of Cyanide-resistant Respiration

Levels of katahdinone (solavetivone), lubimin, rishitin, and phytuberin, sesquiterpenoid stress metabolites of white potato (Solanum tuberosum), were monitored in tuber slices which were challenged with an extract of Phytophthora infestans and incubated under controlled atmospheres. A mixture of ethylene in air enhanced stress metabolite production. This enhancement was amplified by higher partial pressures of oxygen. Stress metabolite production was inhibited by salicylhydroxamic acid. These results suggest the involvement of cyanide-resistant respiration in the production of potato stress metabolites, compounds which may serve as phytoalexins.

Effect of Major Spices in Lebanon Bologna on Acid Production by Starter Culture Organisms

The effect of a Lebanon bologna spice mixture and its major component spices, black pepper, allspice, and nutmeg, on acid production by a mixed starter culture containing Lactobacillus plantarum and Pediococcus cerevisiae was studied in a liquid medium. These spices stimulated acid production by the starter culture organisms although some Lebanon bologna component spices are known to have antimicrobial properties. The spice mixture stimulated L. plantarum more than P. cerevisiae when each organism was cultured singly. Stimulation of acid production could not be attributed solely to differences in bacterial numbers as defined by plate counts.

Destruction of Staphylococcus aureus during frankfurter processing

We studied the thermal resistance of Staphylococcus aureus during frankfurter processing in respect to whether staphylococci are killed by the heating step of the process and whether heat injury interferes with the quantitative estimation of the survivors. With S. aureus 198E, heat injury could be demonstrated only when large numbers of cells (10(8)/g) were present and at a product temperature of 140 degrees F (60 degrees C). On tryptic soy agar and tryptic soy agar plus 7% NaCl media, at temperatures less than 140 degrees F, the counts were virtually identical; above 140 degrees F, the counts converged, with the organisms dying so rapidly that heat injury was not demonstrable. Heat injury was thus judged not to interfere with the quantitative estimation of staphylococci surviving the normal commercial heating given frankfurters. By using a combination of direct plating on tryptic soy agar and a most-probable-number technique, we detected no viable cells (less than 0.3/g) of several strains of S. aureus in frankfurters heated to 160 degrees F (71.1 degrees C). This temperature is compatible with the normal final temperature to which federally inspected processors heat their frankfurters and with the temperature needed to destroy salmonellae.

Destruction of Salmonella and Staphylococcus During Processing of a Nonfermented Snack Sausage

Survival of Salmonella dublin , Salmonella senftenberg 775W, Staphylococcus aureus 196E, and S. aureus 184 was studied during processing of an inoculated beef, nonfermented snack sausage. No viable staphylococci or salmonellae were detected in sausages that had been heated at an internal temperature of 53.9-55.0 C or 57.8-58.9 C for 3.5 h followed by drying at 21 C and 50-55% relative humidity for 4 days. Heating at an internal temperature of 51.1-52.2 C for 3.5 h followed by drying did not produce a salmonellae- or staphylococci-free sausage.

Survival of salmonellae during pepperoni manufacture

Survival of salmonellae in artificially contaminated beef-pork mixtures (approximately 10(4) salmonellae/g) was studied in pepperoni prepared by either a natural flora or lactic starter culture fermentation or in nonfermented sausages. The pepperoni did not become salmonellae free during the usual commercial 15 to 30-day drying period. Salmonella dublin was present in all products, fermented or unfermented, after 42 to 43 days of drying. At a lower level of contamination, 10(3)/g, S. dublin could not be recovered from starter culture-fermented pepperoni after 14 days of drying but persisted in the natural flora-fermented sausage. S. typhimurium (initial count, 10(4)/g) was absent after 42 days of drying when starter culture was used to ferment the pepperoni, but was still present in the natural flora-fermented and unfermented products. S. dublin, host adapted to cattle, or S. choleraesuis, host adapted to swine, had similar survival patterns in beef pork, or beef-pork pepperoni. Heating salmonellae contaminated beef-pork pepperoni (after fermantation but before drying) to an internal temperature of 60 C (trichinae inactivating) eliminated the food-borne pathogen from the sausage product.

Estimating Bacterial Populations in Raw and Simulated Maple Sap by a Modified Resazurin Test

A modified resazurin test was used to estimate bacterial populations growing in natural and simulated maple saps. Comparable results were obtained from both substrates, with a slight decrease in dye reduction time noted when the natural sap substrate was used. Simulated sap could provide a readily available substitute for natural sap in collaborative testing.

SANITATION STUDIES OF A REVERSE OSMOSIS UNIT USED FOR CONCENTRATION OF MAPLE SAP

Sanitation studies of an industrial-scale reverse osmosis unit used for the concentration of maple sap are discussed. Bacterial plate counts of the concentrate and permeate effluent streams declined steadily during the initial 10–12 hr of operation, followed by respective increases in count from 2.8 × 104 per ml (12 hr) to 2.0 × 105 per ml (36 hr) and from 3.3 × 103 per ml (12 hr) to 2.4 × 104 per ml (36 hr). Membrane modules were maintained in good sanitary condition in the reverse osmosis unit pressure vessels for as long as one month when the modules were kept in contact with an acidified chlorine dioxide sanitizer.

Modified Resazurin Test for Estimating Bacterial Population in Maple Sap

The resazurin test for bacterial counts in milk has been modified for estimating the bacterial cells in maple sap. This simple test provides an approximate bacterial cell count in 2–3 hr.

Collaborative Study of a Method and Sampling Techniques For Determining Yeast Count in Maple Sirup

Techniques for sampling and a method for determining the yeast count in maple sirup, studied collaboratively in 1966, have been revised and again studied collaboratively in 18 laboratories. Statistical analysis of collaborators' results indicated that sirup samples shipped in a frozen condition gave more concordant interlaboratory yeast counts. More homogeneous cell suspensions were obtained by mixing the sirup samples warmed to 80 °F with a nonaerating stirrer. The method is recommended for adoption as official, first action.

THE CONTROL OF BACTERIAL CONTAMINATION IN MAPLE SAP STORED IN FIELD STORAGE TANKS BY ULTRAVIOLET IRRADIATION

During the maple sap seasons of 1964 and 1965, sap collected from roadside stands of trees was stored in field holding tanks for as long as eleven days without deterioration, by continually irradiating the stored sap with germicidal ultraviolet lights emitting in the range of 260–300mμ. The bacterial populations of the stored, irradiated sap did not exceed 4.0 × 105 organisms per ml, and sirup made from the sap was light amber in color (fancy grade) with an excellent flavor.