Mark P. Johnson

Microbiological Safety of Cheese Made from Heat-Treated Milk, Part II. Microbiology

A review of epidemiological literature identified six illness outbreaks transmitted via U.S. produced cheese during 40 years, 1948-1988. During these four decades, the United States cheese industry produced over 100 billion pounds of natural cheese (not including cottage and related varieties). The most frequent causative factor in U.S. and Canadian cheese-related outbreaks was post-pasteurization contamination. Faulty pasteurization equipment or procedures were implicated in one outbreak each in the U.S. and Canada. Use of raw milk was a factor in one outbreak in each country. Inadequate time-temperature combinations used for milk heat treatment were not implicated. The epidemiology of cheese-related outbreaks in the U.S., Canada, and Europe demonstrated that soft surface-ripened cheese, e.g. Camembert and Brie, are at significantly greater risk to transmit pathogens than other cheeses. No outbreaks were linked to hard Italian varieties, e.g. Parmesan, Romano, and Provolone. Varieties such as Cheddar and Swiss were infrequently involved. A variety of pathogens have been isolated from raw milk. Some, including Salmonella , Listeria , and enteropathogenic Escherichia coli can survive and grow in some cheeses. In one of the few published studies of milk heat-treatment for cheesemaking, multistrain or species mixtures of pathogens were inoculated into raw milk at levels of 105/ml which was heat-treated in a commercial HTST pasteurizer - mean holding time 17.6 s, minimum 16.2 s. All strains of Yersinia enterocolitica , Campylobacter sp., Escherichia coli 0157:H7, and all but one Salmonella species were destroyed at 65°C (149°F). Salmonella senftenberg (rarely isolated from cheese) was inactivated at 69°C (156.2°F). Listeria monocytogenes in naturally contaminated milk at levels of 104 organisms per ml was inactivated at 66°C (150.8°F); laboratory-cultured inoculum at levels of 105 organisms per ml required 69.0°C (156.2°F). A multiplicity of practices other than pasteurization or heat-treatment contribute significantly to the microbiological safety of cheese. Some, such as milk quality management, lactic culture management, pH control, salt addition, and controlled curing conditions are established technologies. Others represent potential opportunities, such as natural inhibitory substances in milk, antibacterial substances, e.g. nisin and lysozyme.

Protected Areas in Europe

Systematic conservation planning provides a structured, target‐driven approach to ensuring the long‐term maintenance of biodiversity. However, reviews of how well the steps of such a planning process are applied in different regions are scant; some steps may be implemented although there is no formal systematic conservation planning process taking place. Here we conduct such a review for Europe. Taking in turn the six recognized steps of systematic conservation planning, for this region: (i) The availability of data on biodiversity remains a significant constraint on conservation planning because, although species occurrences have often been better mapped in Europe than elsewhere, there is a continuing mismatch between the spatial resolution at which data coverage is adequate and that of habitat fragmentation. (ii) Although there are important legal frameworks for conservation planning, explicit quantitative goals for the representation and persistence of biodiversity are largely lacking. (iii) Assessment of the effectiveness of existing protected area systems is patchy and rather ill developed, with a substantial gulf between the work being conducted in more academic and policy‐oriented arenas. (iv) Nonetheless, particularly through the Natura 2000 process, there has been an extraordinary program to select additional protected areas. (v) Although it has taken longer than originally envisaged, this program is resulting in a substantial expansion of the protected area system. (vi) There are significant concerns over the extent to which existing protected area systems can maintain their biodiversity values, particularly given the small size of many of these areas and likely impacts of climate change.

Microbiological Safety of Cheese Made from Heat-Treated Milk, Part I. Executive Summary, Introduction and History

Research on pasteurization of milk for cheesemaking was begun in the late 1800s. Early equipment was crude and control devices non-existent. Consequently, early pasteurization processes were not well verified. Commercial application was slow, except in New Zealand, where almost the entire cheese industry converted to pasteurization in the 1920s. In the United States, debate on the merits of pasteurization continued for years. Demand for cheese during World War II and foodborne disease outbreaks caused by cheese stimulated promulgation of government standards which included the options of milk pasteurization or 60 d holding at a minimum temperature of 2°C (35°F). The cheese industry has continued to improve technology, including that which is safety related. United States production of cheese has continued to expand, from just over 1 billion pounds in 1948 to 5.4 billion pounds in 1987. Thirty-eight percent of the 1987 total comprised varieties wherein heat-treated milk is frequently utilized.

Macroalgal Introductions by Hull Fouling on Recreational Vessels: Seaweeds and Sailors

Macroalgal invasions in coastal areas have been a growing concern during the past decade. The present study aimed to assess the role of hull fouling on recreational yachts as a vector for macroalgal introductions. Questionnaire and hull surveys were carried out in marinas in France and Spain. The questionnaires revealed that the majority of yacht owners are aware of seaweed introductions, usually undertake short range journeys, dry dock their boat at least once a year, and use antifouling paints. The hull survey showed that many in-service yachts were completely free of macroalgae. When present, fouling assemblages consisted mainly of one to two macroalgal species. The most commonly found species was the tolerant green seaweed Ulva flexuosa. Most of the other species found are also cosmopolitan and opportunistic. A few nonnative and potentially invasive Ceramiales (Rhodophyta) were found occasionally on in-service yachts. On the basis of the information gathered during interviews of yacht owners in the surveyed area, these occurrences are likely to be uncommon. However they can pose a significant risk of primary or secondary introductions of alien macroalgal species, especially in the light of the increase in yachting activities. With large numbers of recreational yachts and relatively rare occurrences of nonnative species on hulls, comprehensive screening programs do not seem justified or practical. The risks of transferring nonnative species may, however, be minimized by encouraging the behaviors that prevent fouling on hulls and by taking action against neglected boats before they can act as vectors.

Beyond the predation halo: small scale gradients in barnacle populations affected by the relative refuge value of crevices

Haloes of bare space around crevices used as refuges by predators are a feature of many rocky shores. The presence of small scale spatial gradients in the demographic structure of prey populations is hypothesized for the region adjoining predation haloes. It is also suggested that halo effects in prey populations will change in response to environmental constraints on predator foraging behaviour. These hypotheses were tested by examining gradients in barnacle population structure around crevices high and low on the shore. The probability of encountering a barnacle above the local median size always increased with distance from a crevice. Foraging at sites high on a shore is assumed to be more risky to individual whelks. Initial probabilities of recording a large barnacle near a crevice increased more rapidly over small spatial scales at sites high on the shore than at sites low on the shore. The implications of small scale gradients in prey populations are discussed with reference to the role of topographic complexity in mediating predator–prey dynamics.

Microbiological Safety of Cheese Made from Heat-Treated Milk, Part III. Technology, Discussion, Recommendations, Bibliography

Heat treatment or pasteurization does not adversely affect the cheesemaking process or the resulting physical properties of the cheese. Both types of heat-treatments can correct chemical changes that occur in cold stored raw milk. Thermization on the farm may help control psychrotrophic bacteria in cold stored milk. Some denaturation of whey protein does occur during pasteurization. Heat treatments slightly above current minimum pasteurization requirements can cause body/texture and moisture control problems in cheese. Loss of functionality can adversely affect the marketing of whey protein products. Cheeses made from pasteurized milk ripen more slowly and usually do not exhibit the flavor intensity of cheeses made from raw or heat-treated milk. Swiss and hard Italian type cheese, whose traditional flavor results in part from native milk enzymes and microflora, would also be adversely affected if milk pasteurization for cheesemaking were mandatory. The quality of cheese made from pasteurized milk is consistently better than cheese made from raw milk as evidenced by fewer body and flavor defects consequent to the growth of undesirable bacteria. Either pasteurization or heat-treatment enables improved uniform process control and quality during cheesemaking. Pathogens were prioritized as high, medium, or low risk in cheese. Three organisms, Salmonella , Listeria monocytogenes and enteropathogenic Escherichia coli were judged to be high risk threats to the cheese industry. Staphylococcus aureus was listed as low risk because growth and toxin production is readily suppressed by lactic cultures and acidity (pH) control in cheese. Three actions are recommended: Establish a guideline for minimum heat-treatment of milk for cheesemaking: 64.4°C (148°F) for 16 s or equivalent with adequate process control. Evaluate current safety technology and practices used for cheese manufacture. Support research with primary emphasis on the combined effect of heat-treatment and other current cheese technologies. Evaluate technologies not currently utilized in cheese manufacture for safety potential.

Comparative genomic analysis reveals species-dependent complexities that explain difficulties with microsatellite marker development in molluscs

Reliable population DNA molecular markers are difficult to develop for molluscs, the reasons for which are largely unknown. Identical protocols for microsatellite marker development were implemented in three gastropods. Success rates were lower for Gibbula cineraria compared to Littorina littorea and L. saxatilis. Comparative genomic analysis of 47.2 kb of microsatellite containing sequences (MCS) revealed a high incidence of cryptic repetitive DNA in their flanking regions. The majority of these were novel, and could be grouped into DNA families based upon sequence similarities. Significant inter-specific variation in abundance of cryptic repetitive DNA and DNA families was observed. Repbase scans show that a large proportion of cryptic repetitive DNA was identified as transposable elements (TEs). We argue that a large number of TEs and their transpositional activity may be linked to differential rates of DNA multiplication and recombination. This is likely to be an important factor explaining inter-specific variation in genome stability and hence microsatellite marker development success rates. Gastropods also differed significantly in the type of TEs classes (autonomous vs non-autonomous) observed. We propose that dissimilar transpositional mechanisms differentiate the TE classes in terms of their propensity for transposition, fixation and/or silencing. Consequently, the phylogenetic conservation of non-autonomous TEs, such as CvA, suggests that dispersal of these elements may have behaved as microsatellite-inducing elements. Results seem to indicate that, compared to autonomous, non-autonomous TEs maybe have a more active role in genome rearrangement processes. The implications of the findings for genomic rearrangement, stability and marker development are discussed.

Fronts, jumps and secondary introductions suggested as different invasion patterns in marine species, with an increase in spread rates over time

Not all introduced (invasive) species in a region will spread from a single point of introduction. Long-distance dispersal or further introductions can obscure the pattern of spread, but the regional importance of such processes is difficult to gauge. These difficulties are further compounded when information on the multiple scale process of invasive species range expansion is reduced to one-dimensional estimates of spread (e.g. km yr−1). We therefore compared the results of two different metrics of range expansion: maximum linear rate of spread and accumulation of occupied grid squares (50 × 50 km) over time. An analysis of records for 54 species of introduced marine macrophytes in the Mediterranean and northeast Atlantic revealed cases where the invasion process was probably missed (e.g. Atlantic Bonnemaisonia hamifera) and suggested cases of secondary introductions or erratic jump dispersal (Dasysiphonia sp. and Womersleyella setacea). A majority of species analysed showed evidence for an accumulation of invaded sites without a clear invasion front. Estimates of spread rate are increasing for more recent introductions. The increase is greater than can be accounted for by temporally varying search effort and implies a historical increase in vector efficiency and/or a decreased resistance of native communities to invasion.

The nutrient economy of a marine inlet: Lough Hyne, South West Ireland

Abstract Simple mass balance models have been frequently used in limnology to study the retention of nutrients by lakes. However, there are difficulties in applying mass balance to marine systems, particularly with regard to parameters involved in tidal flushing. A well defined tidal channel at the entrance to Lough Hyne allows the use of adapted mass balance models to study the nutrient economy, and to make inferences about system scale productivity. Water quality gathered over four years demonstrated a net input to the lough for three different nutrients. There was a net tidal input of dissolved inorganic phosphorus. Significant inputs of dissolved inorganic nitrogen and dissolved inorganic silicon came from freshwater sources. In two of the years a net input of dissolved inorganic nitrogen from the sea was also detected. Scaling the net inputs with flushing terms in a mass balance leads to estimates of the net system productivity. From a dissolved inorganic phosphorus budget, the uptake of nutrient in ...

Like a rolling stone: the mobility of maerl (corallinaceae) and the neutrality of the associated assemblages.

Beds of nonattached coralline algae (maerl or rhodoliths) are widespread and considered relatively species rich. This habitat is generally found in areas where there is chronic physical disturbance such that maerl thalli are frequently moved. Little is known, however, about how natural disturbance regimes affect the species associated with maerl. This study compared the richness, animal abundance, and algal biomass of maerl-associated species over a two-year period in a wave-disturbed bed and a sheltered maerl bed. Changes in associated species over time were assessed for departures from a neutral model in which the dissimilarity between samples reflects random sampling from a common species pool. Algal biomass and species richness at the wave-exposed site and on stabilized maerl at the sheltered site were reduced at times of higher wind speeds. The changes in species richness were not distinguishable from a neutral model, implying that algal species were added at random to the assemblage as the level of disturbance lessened. Results for animal species were more mixed. Although mobile species were less abundant during windy periods at the exposed site, both neutral and non-neutral patterns were evident in the assemblages. Artificial stabilization of maerl had inconsistent effects on the richness of animals but always resulted in more attached algal species. While the results show that the response of a community to disturbance can be neutral, the domain of neutral changes in communities may be relatively small. Alongside non-neutral responses to natural disturbance, artificial stabilization always resulted in an assemblage that was more distinct than would be expected under random sampling from a common pool. Community responses to stabilization treatments did not consistently follow the predictions of the dynamic equilibrium model, the intermediate disturbance model, or a facilitation model. These inconsistencies may reflect site-specific variation in both the disturbance regime and the adjacent habitats that provide source populations for many of the species found associated with maerl.