Ecology of food microorganisms

The behavior of microorganisms in foods is governed by the constraints applied to the microflora by a variety of environmental and ecological factors. These include water activity, pH, E_h, chemical composition, the presence of natural or added antimicrobial compounds, and storage temperature, as well as processing factors such as the application of heat and physical manipulation. Control of these factors will govern whether the food spoils or not, whether any microbial health hazard arises, and whether desired microbial processes are successful or not. While much is known about the effects of individual environmental factors, the effects due to their interactions are less understood. The two main problems now facing the food microbiologist are optimization of environmental parameters and the selection of strains with specific properties. A better understanding of the mechanisms of action and interactions between the various environmental factors, coupled with the application of modern techniques to produce strains with particular properties, will lead to optimum use of food supplies and improvements in quality. There is also potential for the development of new and novel foods.     

Marine microorganisms make a meal of oil

Hundreds of millions of litres of petroleum enter the environment from both natural and anthropogenic sources every year. The input from natural marine oil seeps alone would be enough to cover all of the world's oceans in a layer of oil 20 molecules thick. That the globe is not swamped with oil is testament to the efficiency and versatility of the networks of microorganisms that degrade hydrocarbons, some of which have recently begun to reveal the secrets of when and how they exploit hydrocarbons as a source of carbon and energy.     

Airborne allergenic microorganisms associated with mushroom cultivation

Exposure to microorganisms, including thermophilic actinomycetes and fungal spores, and to airborne dust produced during compost production and mushroom picking may cause work-related respiratory symptoms. Previous studies have implicated Thermoactinomyces vulgaris and Faenia rectivirgula, the aetiological agents in farmer's lung disease, as causes of these symptoms but these species have been rare in aerobiological studies of mushroom farms. As part of a study of the respiratory health of the exposed workers, we carried out an aerobiological survey of all the stages of commercial mushroom production. Samples of viable airborne microorganisms were collected at a farm from eight locations on two occasions using Andersen cascade impactors. Large numbers of airborne thermophilic actinomycetes, yielding > 10⁶ colony-forming units (cfu) m^?3 air sampled, were associated with compost handling. These were predominantly Thermomonospora spp., while Thermoactinomyces spp. and Faenia rectivirgula were few. Because the compost was largely undisturbed, few airborne actinomycete spores were found in mushroom growing houses, but concentrations of fungal spores exceeded 10⁵ cfu m^?3 when mushrooms were being harvested. Most were Penicillium spp. and Aspergillus fumigatus but Peziza ostracoderma and Trichoderma spp. were also isolated. Workers are thus exposed to a wide range of airborne microorganisms, but the role of many of these in mushroom workers' respiratory symptoms is not yet fully understood.     

Ultrastructure of filamentous microorganisms associated with zebra cyathostomes

Filamentous microorganisms were observed colonizing the cuticle of cyathostomes (Nematoda: Strongylidae) collected from the large intestine of Burchell's zebra (Equus burchelli antiquorum). Scanning (SEM) and transmission (TEM) electron microscopy revealed three filamentous microorganisms, designated as segmented, continuous multicellular, and helical. The segmented and continuous multicellular morphotypes each revealed a process of segmentation in their developmental stages, and those of the segmented filaments are demonstrated in this report. In contrast, the helical types of filaments appeared to be complexes of spiraling rodshaped organisms. In addition to these filaments, the cyathostome cuticle was also colonized by other smaller microorganisms.     

Marine microorganisms as a source of bioactive agents

Several ecological factors of the marine environment were used in developing a strategy for discovering useful bioactive agents from marine microorganisms. By consideration of sea water requirements, production and degradation of marine polymers, and plasmid content, several novel anti-malarial antibiotics, anti-tumor polysaccharides, glucan-degrading enzymes, and aminoglycoside antibiotics were found.     

Annual rhythms of swimming behaviour and seawater adaptation in young baltic salmon,Salmo salar,associated with smolting

Synopsis Sexually immature and sexually mature precocious male Baltic salmon,Salmo salar, parr from Umeälven (Ume river) were tested for rheotactic behaviour and adaptation to seawater before, during, and after the time period for smolt migration. Size of fish at the beginning of the experiment in January was on average 13.5 cm. Rheotactic behaviour was tested in annular stream tanks with photocells to measure upstream and downstream movements. Samples of fish were given a Seawater challenge test at monthly intervals in order to determine their ability to adapt to 20%. saltwater. During spring, both immature and sexually precocious parr became silvery and showed progressive development of downstream-directed movements. In early June the fish exhibited good hypoosmoregulatory ability in 20%. saltwater and swimming was predominantly downstream. During late June and early July there was a marked reversal in swimming behaviour, accompanied by a dramatic change in saltwater adaptation. The fish moved mainly upstream and showed decreasing ability to meet the seawater challenge test. This was accompanied by a loss of silvery coloration. The annual cycle of swimming behaviour and seawater adaptation is discussed in relation to the appearance of a smolt-window, i.e., a critical interval for smolt migration.     

Phylogenetic diversity of microorganisms associated with the deep-water sponge Baikalospongia intermedia

The diversity of bacteria associated with deep-water sponge Baikalospongia intermedia was evaluated by sequence analysis of 16S rRNA genes from two sponge samples collected in Lake Baikal from depths of 550 and 1204 m. A total of 64 operational taxonomic units, belonging to nine bacterial phyla, Proteobacteria (classes Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria), Actinobacteria, Planctomycetes, Cloroflexi, Verrucomicrobia, Acidobacteria, Chlorobi, and Nitrospirae, including candidate phylum WS5, were identified. Phylogenetic analysis showed that the examined communities contained phylotypes exhibiting homology to uncultured bacteria from different lake ecosystems, freshwater sediments, soil and geological formations. Moreover, a number of phylotypes were relative to psychrophilic, methane-oxidizing, sulfate-reducing bacteria, and to microorganisms resistant to the influence of heavy metals. It is noted that the unusual habitation conditions of deep-water sponges contribute to the taxonomic diversity of associated bacteria and have an influence on the presence of functionally important microorganisms in bacterial communities.     

Community structure of microorganisms associated with reddish-brown iron-rich snow

Reddish-brown colored snow, containing spherical brown particles, has been observed in several mires in Japan. In order to characterize this remarkable phenomenon, the microbial community and chemical species in snow were analyzed. A core sample of snow which had a colored region was investigated and it revealed vertical shifts in physicochemical characteristics and the microbial community structure. The abundance of particles peaked within the colored layer, and correlated with the amount of reducible Fe(III). The interstitial water of the colored layer was enriched with Fe(II), and characterized by reduced concentration of dissolved methane. The bacterial community in the colored region was characterized by higher relative abundance of iron-reducing bacteria and methanotrophs. Aggregates of the brown particles were found as precipitates in snow melt pools, and were subjected to cloning analyses targeting several different genes. The majority of bacterial 16S rRNA gene clones belonged to the class Betaproteobacteria or the phylum Bacteroidetes. No snow algae were detected in the eukaryotic small subunit rRNA gene clone library. As a possible carbon source to sustain the community in the snow, involvements of carbon dioxide and methane were investigated by analyzing the genes involved in their assimilation. In the analyses of genes for ribulose-1,5-biphosphate carboxylase/oxygenase, clones related to sulfur oxidizers were obtained. The analysis of particulate methane monooxygenase genes indicated dominance of Methylobacter species. These results emphasized the uniqueness of this phenomenon, and iron reducers of the genus Geobacter are suggested to be the key organisms that could be investigated in order to understand the mechanism of this phenomenon.     

Transgenic salmon: tailoring the genome for food production

The production of transgenic salmon using gene transfer technology is described. Both antifreeze proteins and growth hormone genes have been successfully transferred. The expression, inheritance and phenotypes are examined using a wide variety of techniques. The development of new transgenics will be beneficial to aquaculture.     

Bioactive secondary metabolites produced by microorganisms associated with plants

In the past few decades groups of scientists have focused their study on relatively new microorganisms called endophytes. By definition these microorganisms, mostly fungi and bacteria, colonise the intercellular spaces of the plant tissues. The mutual relationship between endophytic microorganisms and their host plants, taxanomy and ecology of endophytes are being studied. Some of these microorganisms produce bioactive secondary metabolites that may be involved in a host-endophyte relationship. Recently, many endophytic bioactive metabolites, known as well as new substances, possesing a wide variety of biological activities as antibiotic, antitumor, antiinflammatory, antioxidant, etc. have been identified. The microorganisms such as endophytes may be very interesting for biotechnological production of bioactive substances as medicinally important agents. Therefore the aim of this review is to briefly characterize endophytes and summarize the structuraly different bioactive secondary metabolites produced by endophytic microorganisms as well as microbial sources of these metabolites and their host plants.     

An annotated checklist of pathogenic microorganisms associated with migratory birds

The potential for transport and dissemination of certain pathogenic microorganisms by migratory birds is of concern. Migratory birds might be involved in dispersal of microorganisms as their biological carriers, mechanical carriers, or as carriers of infected hematophagous ecto-parasites (e.g., ixodid ticks). Many species of microorganisms pathogenic to homeothermic vertebrates including humans have been associated with free-living migratory birds. Migratory birds of diverse species can play significant roles in the ecology and circulation of some arboviruses (e.g., eastern and western equine encephalomyelitis and Sindbis alphaviruses, West Nile and St. Louis encephalitis flaviviruses), influenza A virus, Newcastle disease virus, duck plague herpes-virus, Chlamydophila psittaci, Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato, Campylobacter jejuni, Salmonella enterica, Pasteurella multocida, Mycobacterium avium, Candida spp., and avian hematozoans. The efficiency of dispersal of pathogenic microorganisms depends on a wide variety of biotic and abiotic factors affecting the survival of the agent in, or disappearance from, a habitat or ecosystem in a new geographic area.     

Diversity and biotechnological potential of microorganisms associated with marine sponges

Marine sponges harbor diverse microbial communities, encompassing not only three domains of life including Bacteria, Archaea and eukaryotes, but also many different phyla within Bacteria. This diversity implies a rich source for biodiscovery of new natural products. Here, we review recent progress in our understanding of this genetic diversity, its retrieval via culture and genomic approaches, and its implications for chemical diversity and other biotechnology applications of sponge microorganisms and their genes.     

Marine post-smolt growth and age at maturity of Atlantic salmon

The annual variation in sea-age of maturation for a hatchery dependent stock of Atlantic salmon was compared to variation in post-smolt growth as evidenced by circuli spacing patterns. The proportion of returns of 1-seawinter (1 SW) and 2 SW salmon and the fraction of the smolt year class or cohort that maturated as 1 SW fish, were compared to seasonal growth indices determined from circuli spacing on the scales of smolt class survivors returning as 1 SW and 2 SW spawners. Using image processing techniques, we extracted inter-circuli distances from scales from 2244 recaptured fish. Spacing data for the first year at sea were collected and then expressed as seasonal growth indices for the spring period, when post-smolts first enter the ocean; the summer, when growth appears maximal; and winter, when growth appears to be at a minimum. In general, circuli spacings were wider for 1 SW than for the 2 SW returns of the same smolt cohort. The 1 SW fraction was significantly and positively correlated with late summer growth, suggesting that growth during this season is pivotal in determining the proportion of a smolt class that matures early.     

Ultrastructal morphology of some prokaryotic microorganisms associated with the hindgut of cockroaches.

Scanning electron microscopy and transmission electron microscopy have been used to visualize the morphology and ultrastructure of two types of microorganisms in the hindgut of the cockroach Blaberus posticus. Both organisms, designated as either short or long rods, are attached to chitinous projections from the gut wall. Micrographs suggest that the organisms are prokaryotic with a cell wall complex characteristic of gram-negative bacteria. However, certain differences were noted between the cell wall complex of the two types. Two forms of the long-rod type were noted, with one form appearing to be a "degenerate" or "transitional" cell. In the degenerate cells, vesicles are observed that often are contiguous with the cytoplasmic membrane. There are indications that the long-rod type may divide by longitudinal fission. Neither the short- nor long-rod type has been cultivated in its respective recognizable form.     

Chymotrypsin-like protease activity associated with demembranated sperm of chum salmon.

Our previous study suggested that a chymotrypsin-like protease was involved in the motility of chum salmon sperm (Inaba K, Morisawa M, Biomed Res (1991) 12, 435-437). In this study, we examined the peptidase activity of demembranated sperm of chum salmon using ten synthetic peptides. When spermatozoa were treated with 0.04% Triton X-100 for extracting the plasma membrane and the suspension was separated into the Triton-soluble and insoluble fractions by centrifugation, only the hydrolytic activity towards succinyl (Suc)-Leu-Leu-Val-Tyr-4-methylcoumaryl-7-amide (MCA), a typical substrate for chymotrypsin-like protease, was mostly retained in the insoluble fraction. The bulk of the activities toward other substrates was detected in the soluble fraction. Flagellar axonemes isolated from demembranated sperm showed considerable hydrolytic activity toward Suc-Leu-Leu-Val-Tyr-MCA and the activity was still retained in the axoneme even after further washing. The hydrolysis was activated by a low concentration of SDS, suggesting that the protease associated with the axonemes is a multicatalytic ATP-dependent proteinase (proteasome). Motility of demembranated sperm was inhibited by Suc-Leu-Leu-Val-Tyr-MCA in an ATP-concentration-dependent manner. These results suggest that proteasomes associated with flagellar axoneme regulate flagellar motility.