Changes in microbial population during fermentation of feedlot waste with corn

A new process for recycling feedlot waste involves the fermentation of liquid from this waste combined with corn. Changes in the flora of this silage-like fermentation were followed. The fermentation was dominated by lactobacilli and yeasts, which initially constitute 1% or less of the natural flora. The species of yeasts and lactics involved were characterized. The fermentation has two phases. A single heterolactic species multiplied rapidly for the first 24 h until it represented 95% of the lactobacilli and more than 90% of the total microflora. It displaced the betabacterium predominant among lactics of the original waste; the acid produced killed coliforms and other organisms in feedlot waste; and the acetic acid produced probably caused the death of the dominant native yeast Trichosporon cutaneum (de Beurm., Gougerot et Vaucher) Ota. The peak lactobacillus count remained constant (about 2 × 10⁹ organisms/g [wet weight]) throughout the rest of the fermentation. Homolactics dominated the later phase and yeasts increased to 9.5 × 10⁷ organisms/g (wet weight). At 6 days, a stable mixture of three lactobacilli was present, one streptobacterium, one thermobacterium, and one betabacterium. Similarly, yeasts stabilized as a mixture of two Candida sp. and one Pichia sp. The dominant species of lactics were characterized. Information on the sequence of microorganisms provides a basis for enhanced protein synthesis in the fermentation.     

Changes in freshwater bacterial community composition during measurements of microbial and community respiration

The respiration rates of a pelagic community and of its microbialfraction (< 1.2 µm) were measured at two depths inthe oxic layer of a meromictic alpine lake (Cadagno, Switzerland)using the oxygen technique. The duration of the incubationswere 12, 24 and 55 h. Bacterioplankton abundance (DAPI counts)and composition (whole cell hybridization using 11 group-specificrRNA-targeted oligonucleotide probes) were measured during theincubations. Respiration generally increased with time, especiallyin the microbial fraction, or remained similar. This resultwas not always consistent with changes in bacterial abundanceand cell volume. The composition of the community also changedduring the incubations. The abundance of ß-Proteobacteriaincreased during the course of all the experiments. These resultsextend the previous conclusions drawn in marine environmentsto fresh waters and demonstrate that, in addition to changesin bacterial abundance, cell volume and biomass, changes inthe taxonomic composition of the bacterial community can occurduring discrete incubations of freshwater planktonic communities.     

Swamp-riverine tropical fish population: a comparative study of two spatially isolated freshwater ecosystems in Peninsular Malaysia

Twenty-four fish species were collected during a study from October 1996 of the swamp-riverine fish populations of two spatially isolated Malaysian freshwater swamp ecosystems. Twenty one species were collected from the Beriah Kanan River, which is located in northern Peninsular Malaysia, compared to only 10 species obtained from the Ulu Sedili River in the south. At both sites, the species Rasbora einthovenii and Hemirhamphodon pogognathu appeared to be the most dominant species, whereas Rasbora pauciperforata and Nemacheilus selangoricus were very rarely caught and Beriah Kanan and Ulu Sedili River, respectively. An analysis of the physico-chemical data showed that although pH, conductivity and ammonium levels were fairly similar at both sites, orthophosphate, hardness and total suspended solids were relatively higher for Ulu Sedili River.     

Swamp-riverine tropical fish population: a comparative study of two spatially isolated freshwater ecosystems in Peninsular Malaysia

Twenty-four fish species were collected during a study from October 1996 of the swamp-riverine fish populations of two spatially isolated Malaysian freshwater swamp ecosystems. Twenty one species were collected from the Beriah Kanan River, which is located in northern Peninsular Malaysia, compared to only 10 species obtained from the Ulu Sedili River in the south. At both sites, the species Rasbora einthovenii and Hemirhamphodon pogognathu appeared to be the most dominant species, whereas Rasbora pauciperforata and Nemacheilus selangoricus were very rarely caught and Beriah Kanan and Ulu Sedili River, respectively. An analysis of the physico-chemical data showed that although pH, conductivity and ammonium levels were fairly similar at both sites, orthophosphate, hardness and total suspended solids were relatively higher for Ulu Sedili River.     

Studies on the bottom fauna in a tropical freshwater fish pond

Summary Quantitative samples of the bottom fauna obtained from a tropical freshwater fish pond during a period of two years were studied with regard to species composition, zonal variation and seasonal fluctuation. Two different zones with differences in faunal composition could be distinguished. The littoral zone was dominated by Mollusca, whereas Oligochaetes were predominant in the profundal zone. Most of the organisms showed their peaks in the months January to April. Breeding activities ofVivipara bengalensis, Digoniostoma cerameopoma, Melanoides granifera andPisidium clarkeanum as evidenced by presence of younger length groups in the populations were also observed during the same period (January to April). The influence of environmental factors as temperature, alkalinity and food were discussed as probable causes for the peaks in abundance. The average number of total organisms per square metre was found to be comparatively high indicating a high standing crop. Differences observed in the total number of organisms present have been attributed to inflow of water resulting in sudden alteration of the nutrient condition of the bottom mud. The seasonal variations of the standing crop of bottom fauna during both the years have been found to be influenced by fluctuations of the bivalve mollusc,Lamellidens corrianus. The availability of sufficient amount of benthic fauna for consumption by bottom feeding fishes has been indicated.This work formed part of a thesis submitted for the Degree of Doctor of Philosophy to the University of Calcutta, India in 1964.     

Changes in microbiota population during fermentation of narezushi as revealed by pyrosequencing analysis

Modern Japanese sushi is derived from an archetype, narezushi, which is made by the fermentation of salted fish with rice. Several studies have demonstrated that lactic acid bacteria are dominantly present in narezushi, but no studies have addressed how microbial composition changes during fermentation. In this study, we examined changes in the microbial population in aji (horse mackerel)-narezushi during fermentation by pyrosequencing the 16S ribosomal RNA gene (rDNA). Ribosomal Database Project Classifier analysis revealed that among the 53 genera present, the Lactobacillus population drastically increased during fermentation, while the populations of other bacteria remained unchanged. Basic Local Alignment Search Tool analysis revealed that L. plantarum and L. brevis were the major species. Comparison with other fermented food microbiota indicated high product-dependency of the bacterial composition, which might have been due to the starter-free fermentation process.     

Mechanisms of maintenance of tropical freshwater fish communities in the face of disturbance

Community resistance to, and resilience from, perturbation will determine the trajectory of recovery from disturbance. Although selective timber extraction is considered a severe disturbance, fish communities from headwater streams around Danum Valley Field Centre, Sabah, Malaysia, showed few long-term changes in species composition or abundance. However, some species showed short-term (< 18 months) absence or decrease in abundance. These observations suggested that both resistance and resilience were important in maintaining long-term fish community structure. Resistance to perturbation was tested by monitoring fish communities before and after the creation of log-debris dams, while resilience was investigated by following the time-course of recolonization following complete removal of all fish. High community resistance was generally shown although the response was site-specific, dependent on the composition of the starting community, the size of the stream and physical habitat changes. High resilience was demonstrated in all recolonization experiments with strong correlations between pre- and post-defaunation communities, although there was a significant difference between pool and riffle habitats in the time-course of recovery. These differences can be explained by the movement characteristics of the species found in the different habitats. Resilience appeared to be a more predictable characteristic of the community than resistance and the implications of this for ensuring the long-term persistence of fish in the area are discussed.     

Studying the dynamics of microbial populations during food fermentation

The dynamics of growth, survival and biochemical activity of microorganisms in food are the result of stress reactions in response to the changing of the physical and chemical conditions into the food microenvironment, the ability to colonise the food matrix and to growth into a spatial heterogeneity, and the in situ cell-to-cell ecological interactions which often happen in a solid phase. In food, ecological approaches to study the evolution of microbial flora would be useful to comprehend better the microbiological processes involved in food processing and ripening, to improve microbiological safety by monitoring in situ pathogenic bacteria, and to evaluate the effective compositions of the microbial populations. This paper gives a general overview of biotechnological approaches to study microbial populations in food fermentation.     

Citogenetic characterization of the tropical freshwater fish Parachromis managuensis (Pisces: Cichlidae)

To describe the cytogenetics of the jaguar cichlid fish Parachromis managuensis, we collected eight males and 13 females in Villahermosa, Tabasco, México. The specimens were processed with standard cytogenetic techniques (slightly modified), and high quality fields of chromosomes in mitosis and meiosis were obtained; 14 of these fields were analyzed by meristics and statistics methods. The specimens presented a diploid modal number of 2n = 48 chromosomes, which is similar to the number reported for others Central American cichlids; five pairs were submetacentric-metacentrics (biarmed) and 19 were subtelocentric-telocentric (uni-armed), giving a fundamental number (NF) of 58. The haploid number was confirmed by counting meiotic fields in metaphase I. There was not evidence of heteromorphism: sexual chromosomes were not identifiable.     

Changes in the microbial community during repeated anaerobic microbial dechlorination of pentachlorophenol

Pentachlorophenol (PCP) has been widely used as a pesticide in paddy fields and has imposed negative ecological effect on agricultural soil systems, which are in typically anaerobic conditions. In this study, we investigated the effect of repeated additions of PCP to paddy soil on the microbial communities under anoxic conditions. Acetate was added as the carbon source to induce and accelerate cycles of the PCP degradation. A maximum degradation rate occurred at the 11th cycle, which completely transformed 32.3 μM (8.6 mg L^?1) PCP in 5 days. Illumina high throughput sequencing of 16S rRNA gene was used to profile the diversity and abundance of microbial communities at each interval and the results showed that the phyla of Bacteroidates, Firmicutes, Proteobacteria, and Euryarchaeota had a dominant presence in the PCP-dechlorinating cultures. Methanosarcina, Syntrophobotulus, Anaeromusa, Zoogloea, Treponema, W22 (family of Cloacamonaceae), and unclassified Cloacamonales were found to be the dominant genera during PCP dechlorination with acetate. The microbial community structure became relatively stable as cycles increased. Treponema, W22, and unclassified Cloacamonales were firstly observed to be associated with PCP dechlorination in the present study. Methanosarcina that have been isolated or identified in PCP dechlorination cultures previously was apparently enriched in the PCP dechlorination cultures. Additionally, the iron-cycling bacteria Syntrophobotulus, Anaeromusa, and Zoogloea were enriched in the PCP dechlorination cultures indicated they were likely to play an important role in PCP dechlorination. These findings increase our understanding for the microbial and geochemical interactions inherent in the transformation of organic contaminants from iron rich soil, and further extend our knowledge of the PCP-transforming microbial communities in anaerobic soil conditions.     

Taxonomic distinctness in a linear system: a test using a tropical freshwater fish assemblage

Taxonomic distinctness, a measure of diversity that captures the phylogenetic relatedness of an assemblage, has been successfully applied in several marine communities and appears to have considerable potential for environmental assessment and conservation. This approach has, however, not hitherto been used in structured freshwater systems. We evaluated this technique in the context of vulnerable tropical river drainages in India. We found that the inherent physical structure of river systems and longitudinal gradients in habitat characteristics influenced the pattern of taxonomic distinctness. Downstream locations were in general more taxonomically diverse than upstream ones. This in turn means that highly perturbed sites in the lower reaches of rivers would not display a reduction in taxonomic distinctness relative to a random expectation. The utility of the approach for detecting habitat and other disturbances on stream fish communities is thus limited. Implications of these unique properties of river ecosystems and their communities to conservation are discussed.     

Variation in microbial population during composting of agro-industrial waste

Two compost piles were prepared, using two ventilation systems: forced ventilation and ventilation through mechanical turning. The material to compost was a mixture of orange waste, olive pomace, and grass clippings (2:1:1 v/v). During the composting period (375 days), samples were periodically taken from both piles, and the enumeration of fungi, actinomycetes, and heterotrophic bacteria was carried out. All studied microorganisms were incubated at 25 and 55 °C after inoculation in appropriate growth media. Fungi were dominant in the early stages of both composting processes; heterotrophic bacteria proliferated mainly during the thermophilic stage, and actinomycetes were more abundant in the final stage of the composting process. Our results showed that the physical and chemical parameters: temperature, pH, moisture, and aeration influenced the variation of the microbial population along the composting process. This study demonstrated that composting of these types of wastes, despite the prolonged mesophilic stage, provided an expected microbial variation.     

Changes in microbial populations during anaerobic flax retting

D onaghy , J.A., L evett , P.N. & H aylock , R.W. 1990. Changes in microbial populations during anaerobic flax retting. Journal of Applied Bacteriology 69 , 634–641.
The bacterial flora of industrial and laboratory scale anaerobic flax rets were determined at intervals throughout the rets. Although after an initial lag period total bacterial numbers remained roughly constant there were fluctuations in the bacterial species constituting the total. Pure culture rets and enzyme assays were used to determine which strains had retting potential. Of the strains demonstrated to have retting ability Bacillus licheniformis and B. subtilis were numerically dominant from 10 to 40 h and were succeeded in dominance by Clostridium acetobutylicum and Cl. felsineum .     

River drying influences genetic variation and population structure in an Arctic freshwater fish

Conserving biodiversity in an era of rapid climate change requires understanding the mechanisms that influence dispersal, gene flow and, ultimately, species persistence. This information is becoming critical for conserving key species in rapidly warming places such as the Arctic. Arctic freshwater fish not only face warmer conditions, but also the drying of tundra streams due to climate change. Here, we examined population structure, gene flow, and the influence of landscape features on the neutral genetic variation of the Arctic grayling on Alaska’s North Slope. We estimated the number of genetically distinct clusters and determined effective population sizes for and patterns of gene flow among geographic regions. We predicted that river distance, river drying, distance to the coast, and elevational gradient would influence genetic differentiation for Arctic grayling. Bayesian clustering and discriminant analysis of principal components found support for five or six genetic clusters roughly corresponding to downstream and headwater subwatersheds. Estimates of gene flow revealed asymmetric downstream bias. River distance and river dry zones were significantly associated with increasing genetic differentiation among sampling locations despite this species' high dispersal capability and the temporary nature of dry zones. Isolation and downstream-biased dispersal could contribute to high levels of inter-population genetic variation among the headwaters of the North Slope Arctic grayling metapopulation, which might be particularly important for species conservation during rapid climate change. More generally, small, isolated populations might drive particular alleles to higher frequencies due to selection or drift, thus promoting the genetic potential for rapid evolutionary changes under future climate change.

     

Population cycles in freshwater fish

Year-class strength in fish populations frequently follows an erratic pattern. However, predictable cyclic fluctuations in recruitment have been reported in a number of instances. In fish in which a single age-class is responsible for all or most of the production of eggs, a cycle may be set up with a period equal to the time taken to reach maturity. Moreover, density-dependence may act through fecundity or via survival of eggs or fish subject to interactions with predators or competitors. This paper reviews examples of cyclic variation in year-class strength and discusses the range of underlying causes.