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PubMedDate not supplied

Chaos and order in plankton dynamics. Complex behavior of a simple model.

The role of the diffusive interaction between fish-populated and fish-free habitats in a patchy environment in plankton pattern formation is studied by means of a minimal reaction-diffusion model of the nutrient-plankton-fish food chain. It is shown that such interaction can give rise to spatio-temporal plankton patterns. The fractal dimension of the patterns is shown dependent on the fish predation rate. The spatially averaged plankton dynamics depending on both fish predation rate and distance between fish-populated habitats can exhibit chaotic and regular behavior. The chaotic plankton dynamics is characteristic of a wide parameter range.

Animals↗
PubMed2004

Seasonal variation in plankton community responses of mesocosms dosed with pentachlorophenol.

Seasonal variations in plankton community response to pentachlorophenol (PCP) were studied in four mesocosm experiments using enclosures in a small lake. The mesocosms (860 l) were dosed with single applications of technical grade PCP (0, 4, 10, 24, 36, 54, 81 and 121 microg/l PCP) and monitored for 20 days. Multivariate statistical analyses showed that plankton community taxonomic composition varied with season. In winter and spring, communities were most stable in time; species diversity and abundance were lowest in winter. Seasonally, the communities varied little with respect to the dominant species, which were the copepod Calamoecia lucasi, the alga Peridinium sp. and the rotifer Ascomorpha ovalis. The direct effects of the PCP additions varied little between seasons, but indirect effects were evident at lower treatment levels in autumn. Indirect effects were not evident in winter. Minor variations in plankton community responses to PCP with season were apparent in the following order of decreasing sensitivity; autumn > or = winter/spring > or = summer. At the species level, C. lucasi showed the largest response. The responses observed were greatest in autumn, with decreased abundance at PCP concentrations > or = 24 microg/l. In the other seasons, effects were observed at levels of 54 or 81 microg/l and higher. Ascomorpha ovalis was the most responding rotifer in winter and spring, whereas Anuraeopsis fissa responded more strongly in autumn and summer. The dinoflagellate alga Peridinium sp. had the largest negative response in all but winter, when Dinobryon cylindricum did. Cryptomonas sp. responded positively to PCP in all seasons, increasing in abundance in the highest treatments, possibly due to reduced grazing pressure, reduced competition, or increased decomposition. The plankton community no-observed effect-concentration (NOEC) was 24-36 microg/l PCP. Results reported here suggest that the Australian and New Zealand water quality guideline values for PCP are sufficient to protect plankton communities against adverse effects.

Animals↗
PubMed2005

Role of two toxin-producing plankton and their effect on phytoplankton-zooplankton system--a mathematical study supported by experimental findings.

Plankton is the basis of the entire aquatic food chain. Phytoplankton, in particular, occupies the first trophic level. Plankton performs services for the Earth: it serves as food for marine life, gives off oxygen and also absorbs half of the carbon dioxide from the Earth's atmosphere. The dynamics of a rapid (or massive) increase or decrease of plankton populations is an important subject in marine plankton ecology and generally termed as a 'bloom'. Harmful algal blooms (HABs) have adverse effects on human health, fishery, tourism, and the environment. In recent years, considerable scientific attention has been given to HABs. Toxic substances released by harmful plankton play an important role in this context. In this paper, a mathematical model consisting of two harmful phytoplankton and zooplankton system will be discussed. The analytical findings will be verified through our experimental observations which were carried out on the eastern part of Bay of Bengal for the last three years.

Animals↗
PubMed2001

Comparative antimicrobial activities of antiseptic mouthrinses against isogenic planktonic and biofilm forms of Actinobacillus actinomycetemcomitans.

BACKGROUND: Bacteria contained in biofilms have been shown to have a decreased susceptibility to antimicrobial agents compared to those in planktonic form. Thus, in vitro biofilm models have been developed for screening oral antimicrobial formulations in an effort to produce findings more predictive of clinical activity. This study compared the antimicrobial activity of three mouthrinse formulations when tested against isogenic strains of Actinobacillus actinomycetemcomitans (Aa), one of which was a clinical isolate which forms tenacious biofilms in vitro and the other of which was a spontaneous variant which always grows planktonically. METHOD: Biofilm-forming Aa strains CU1000 and NJ4300, obtained as clinical isolates, and their respective spontaneous planktonic variants, CU1060 and NJ4350, were grown under standard laboratory conditions and exposed for 15 s to either a negative control (phosphate buffered saline [PBS]), an essential-oil containing mouthrinse (Listerine Antiseptic [LA]), an amine fluoride/stannous fluoride-containing mouthrinse (Meridol [M]), or a triclosan and PVM/MA copolymer-containing mouthrinse (Plax [P]). The cells were then washed, serially diluted, plated, and incubated for enumeration of viable bacteria. Colony-forming units (CFU)/ml were log10 transformed and the mouthrinse groups were compared to the PBS group using analysis of variance. RESULTS: All 3 mouthrinses produced statisically significant 99.99% reductions (p< or =0.0001) in both planktonic strains compared to the PBS control. Effects on the biofilm forms of the organisms were more variable. Exposure to LA produced statistically significant (p< or =0.0001) reductions in strains CU1000 and NJ4300 of 98.20% and 96.47%, respectively, compared to PBS. M and P produced much smaller reductions which were not statistically significant. CONCLUSIONS: The results of this study, in which antimicrobial mouthrinses were tested against biofilm-forming and planktonic strains of the same organism, provide a clear demonstration of the resistance to antimicrobial agents conferred by biofilm formation and provide additional support for employing tests using biofilms to more accurately assess the relative activities of antiplaque agents in vitro.

Aggregatibacter actinomycetemcomitans↗
PubMed2002

rDNA analyses of planktonic heterocystous cyanobacteria, including members of the genera Anabaenopsis and Cyanospira.

The taxonomic coherence and phylogenetic relationships of 11 planktonic heterocystous cyanobacterial isolates were examined by investigating two areas of the rRNA operon, the 16S rRNA gene (rrnS) and the internal transcribed spacer (ITS) located between the 16S rRNA and 23S rRNA genes. The rrnS sequences were determined for five strains, including representatives of Anabaena flos-aquae, Aphanizomenon flos-aquae, Nodularia sp. and two alkaliphilic planktonic members of the genera Anabaenopsis and Cyanospira, whose phylogenetic position was previously unknown. Comparison of the data with those previously published for individual groups of planktonic heterocystous cyanobacteria showed that, with the exception of members assigned to the genus Cylindrospermopsis, all the planktonic strains form a distinct subclade within the monophyletic clade of heterocystous cyanobacteria. Within this subclade five different phylogenetic clusters were distinguished. The phylogenetic groupings of Anabaena and Aphanizomenon strains within three of these clusters were not always consistent with their generic or specific assignments based on classical morphological definitions, and the high degree of sequence similarity between strains of Anabaenopsis and Cyanospira suggests that they may be assignable to a single genus. Ribotyping and additional studies performed on PCR amplicons of the 16S rDNA or the ITS for the 11 planktonic heterocystous strains demonstrated that they all contain multiple rrn operons and ITS regions of variable size. Finally, evidence is provided for intra-genomic sequence heterogeneity of the 16S rRNA genes within most of the individual isolates.

Base Sequence↗
PubMed2004

Detection of free and plankton-associated Helicobacter pylori in seawater.

AIMS: To detect both free and plankton-associated Helicobacter pylori in seawater samples collected on the Italian coast of the Adriatic Sea using a nested-PCR. METHODS AND RESULTS: Dissolved oxygen, pH, salinity and chlorophyll 'a' were the parameters recorded together with the characterization of zooplanktonic organisms. Plankton-associated H. pylori DNA was searched for in water samples filtered through 200 and 64 microm nylon nets whereas free bacteria were retained with the subsequent filtration through 0.22 microm pore-size membranes. Nested-PCR using primers for the glmM (ureC) gene was performed to reveal the presence of H. pylori. The DNA sequencing of amplified products confirmed the specificity of the assay. The sensitivity of the nested-PCR assay for H. pylori detection was 62 CFU per 100 ml in spiked water samples. Helicobacter pylori either free or bound to planktonic organisms was found in seven of 12 monthly samples. In particular, free bacteria were detected during the summer sampling and in November, December and March associated to planktonic cells. CONCLUSIONS: The presence of free and plankton-associated H. pylori in seawater suggests that it can be a significant reservoir and a potential route of transmission for the microorganism. SIGNIFICANCE AND IMPACT OF THE STUDY: Our study seems to provide a promising background to define new and effective strategies for surveillance of this human pathogen.

Animals↗
PubMedDate not supplied

Comparisons of the susceptibilities of planktonic and adherent Candida albicans to antifungal agents: a modified XTT tetrazolium assay using synchronised C. albicans cells.

Adhesion of synchronised yeast-phase Candida albicans cells to tissue culture plastic, and the susceptibility of planktonic and adherent cells to antifungal agents, was investigated using a modified tetrazolium (XTT) assay. MIC data demonstrated that ketoconazole and amphotericin B were highly active against planktonic C. albicans yeast-phase cells. XTT tetrazolium assays permitted comparisons of MIC values with XTT formazan IC50 and IC80 (percentage inhibitory concentrations); IC50 and IC80 values for amphotericin B and ketoconazole were similar. Furthermore, IC50 and IC80 values for 24 h incubation with antifungal agent were typically higher than corresponding IC50 and IC80 values for 48 h incubation. Furthermore, in comparison to values for planktonic Candida cells, adherent cells were typically less susceptible to amphotericin B and ketoconazole. For example, with increasing incubation time following the initial adhesion period, cells became progressively less susceptible to amphotericin B and ketoconazole: 24 h (P < 0.05) and 48 h (P < 0.001). Furthermore, other azoles showed the same activities compared with ketoconazole against both planktonic and adherent cells. Overall, the data demonstrate the usefulness of the XTT tetrazolium assay in describing comparisons of the susceptibility profiles for both planktonic and adherent synchronous yeast phase C. albicans in vitro.

Amphotericin B↗
PubMed1998

Chaos and peak-to-peak dynamics in a plankton-fish model.

A plankton-fish model, comprising phosphorus, algae, zooplankton, and young fish, with light intensity and water temperature varying periodically with the seasons, is analyzed in this paper. For realistic values of the parameters the model behaves chaotically, but its dynamics within the strange attractor can be described by a few one-dimensional maps that allow one to forecast the next yearly peak of plankton or fish from the last peaks. This property is an unambiguous mark of a special form of chaos. Unfortunately, the estimate of such peak-to-peak maps from field data is possible only if plankton or young fish biomass has been sampled accurately and frequently for a paramount number of years. In conclusion, the analysis shows that it might be that plankton dynamics are characterized by an interesting and peculiar form of chaos, but that inferences from recorded data on the existence of these forms of chaos are premature.

Animals↗
PubMed2000

Determination of trace elements in marine plankton by inductively coupled plasma mass spectrometry (ICP-MS).

A method has been developed for the determination of 23 elements in marine plankton in which inductively coupled plasma (ICP) source mass spectrometry (MS) was used to quantify the elements in the solution after digestion in a mixture of hydrofluoric and nitric acids in sealed PTFE vessels in a microwave field. The procedure was validated by the analysis of a standard reference soil (SRM 2709 San Joaquin Soil) and a standard reference fresh water plankton (CRM 414). The method was applied to the analysis of several marine plankton samples grown under controlled conditions including several whose growth media had been enriched with selenium. Matrix induced signal suppressions and instrumental drift were corrected by internal standardization. The suitabilities of germanium, indium, rhodium, scandium and yttrium as internal standard elements were evaluated. Neither scandium nor yttrium could be used due to the presence of these elements in the samples, germanium was used for the determination of As, Co, Cu, Fe, Ni, Se, Si and Zn, indium was used for Al, Ba, Ca, Eu, Sr, and Tl, and rhodium was used for Cd, Cr, Hg, Mg, Pb, Sb, Sn, and V. For Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Si, Sr, V, and Zn internal standardization did not completely compensate for the suppressive effect of the heavier elements and the solutions were diluted. However, for As, Ba, Cd, Co, Eu, Hg, Pb, Sb, Se, Sn and T1, it was possible to obtain accurate results despite the 35-40% suppression in the signals. Isobaric overlap was only a problem in the cases of 42Ca and 78Se; 44Ca and 77Se, respectively, were used. Memory effects were only observed with Hg for which a nitric acid-sodium chloride solution was the most effective wash-out solution. The marine plankton samples were able to tolerate a higher concentration of Hg as the selenium concentration increased.

Animals↗
PubMed2006

The mixotroph Ochromonas tuberculata may invade and suppress specialist phago- and phototroph plankton communities depending on nutrient conditions.

Mixotrophic organisms combine light, mineral nutrients, and prey as supplementary resources. Based on theoretical assumptions and field observations, we tested experimentally the hypothesis that mixotrophs may invade established plankton communities depending on the trophic status of the system, and investigated possible effects on food web structure, species diversity, and nutrient dynamics. To test our hypothesis, we inoculated the mixotrophic nanoflagellate Ochromonas tuberculata into established planktonic food webs, consisting of specialist phototrophs, specialist phagotrophs, and bacteria at different supplies of soluble inorganic nutrients and dissolved organic carbon. Oligotrophic systems facilitated the invasion of O. tuberculata in two different ways. First, the combination of photosynthesis and phagotrophy gave mixotrophs a competitive advantage over specialist phototrophs and specialist phagotrophs. Second, low nutrient supplies supported the growth of small plankton organisms that fell into the food size spectrum of mixotrophs. Conversely, high nutrient supplies prevented O. tuberculata from successfully invading the food webs. Two important conclusions were derived from our experiments. First, in contrast to a paradigm of ecology, specialization may not necessarily be the most successful strategy for survival under stable conditions. Indeed, the use of several resources with lower efficiency can be an equally, or even more, successful strategy in nature. Second, when limiting nutrients promote the growth of bacterio- and picophytoplankton, invading mixotrophs may have a habitat-ameliorating effect for higher trophic levels, gauged in terms of food quantity and quality. Using given resources more efficiently, O. tuberculata generated higher biomasses and expressed an increased nutritional value for potential planktivores, due to decreased cellular carbon to phosphorus (C:P) ratios compared to specialized plankton taxa. Our findings may help to explain why energy transfer efficiency between phytoplankton and higher trophic levels is generally higher in oligotrophic systems than in nutrient rich environments.

Animals↗
PubMed2005

Effect of oxygen limitation on the in vitro antimicrobial susceptibility of clinical isolates of Pseudomonas aeruginosa grown planktonically and as biofilms.

Pseudomonas aeruginosa, the predominant causative pathogen of chronic lung infection in patients with cystic fibrosis, may grow under anaerobic conditions as biofilms in the lungs of cystic fibrosis patients. To determine if growth under anaerobic conditions affects the antimicrobial susceptibility of P. aeruginosa, the susceptibility of clinical isolates of P. aeruginosa grown planktonically and as biofilms to a range of antibiotics was determined. Growth under anaerobic conditions did not reduce the ability of ceftazidime, meropenem, aztreonam, piperacillin, or piperacillin/tazobactam to inhibit planktonic growth, with MIC50 values for these antibiotics remaining unchanged or decreasing. However, tobramycin was less effective at inhibiting planktonic bacterial growth under anaerobic conditions, with the MIC50 of tobramycin increasing twofold. Growth under anaerobic conditions also decreased the bactericidal activity of tobramycin, with the MBC50 of tobramycin increasing fourfold. The killing kinetics of tobramycin was also examined under aerobic and anaerobic conditions for selected isolates. When isolates 6A and 12A were grown aerobically, concentration-dependent decreases in total viable count were apparent with tobramycin. In contrast, when these isolates were grown anaerobically, tobramycin at the same concentrations did not decrease the total viable count. When isolates were grown as biofilms under both aerobic and anaerobic conditions, isolate- and concentration-dependent differences in killing of the biofilms by tobramycin were apparent. However, tobramycin at concentrations up to 128 mg/l was unable to eradicate biofilms of any of the isolates tested, whether biofilms were grown aerobically or anaerobically. These results show that oxygen limitation may reduce, in a strain-dependent manner, the susceptibility to tobramycin of P. aeruginosa grown planktonically and as biofilms.

Aerobiosis↗
PubMed2004

delta-Aminolaevulinic acid mediated photodynamic antimicrobial chemotherapy on Pseudomonas aeruginosa planktonic and biofilm cultures.

To demonstrate photodynamic antimicrobial chemotherapy (PACT) against planktonic and biofilm cultures of Pseudomonas aeruginosa, using photoporphyrin IX which could be endogenously synthesized by administrating delta-aminolaevulinic acid (delta-ALA), and a light emitted diode (LED) array to photoactivate the photosensitizer. P. aeruginosa suspended cells or biofilms, grown on a rotating disk reactor, were treated by different concentrations of delta-ALA in the dark for 1 h, followed by LED irradiation for various time. Regrowth experiments were conducted by placed PACT-treated disks back to a sterile reactor. Viable cells were determined by serial dilution and plate counts. Both P. aeruginosa planktonic and biofilm cells were inhibited by PACT with light doses or photosensitizer concentrations increasing. Treatments of planktonic cells with 10 mM delta-ALA and incident dose 240 J cm(-2) or 7.5 mM ALA and incident dose 360 J cm(-2) led to completely photoinactivation. No viable biofilm cells were found after treatment of 20 mM delta-ALA and incident dose 240 J cm(-2). However, regrowth was observed once PACT-treated biofilms were put back to a sterile reactor. Regrowth could be prevented only if biofilm samples were treated PACT twice. delta-ALA-mediated PACT on P. aeruginosa planktonic and biofilm cells was effective, though the detailed mechanism still required further investigation.

Aminolevulinic Acid↗
PubMed2006

Fingerprinting petroleum hydrocarbons in plankton and surface sediments during the spring and early summer blooms in the Galician coast (NW Spain) after the Prestige oil spill.

Plankton samples (20-350 microm and >350 microm) collected at three transects along the Galician coast (NW Spain) were analysed for individual aliphatic and aromatic hydrocarbons by GC-MS. Sample collection was performed in April-July 2003, after the Prestige oil spill (November 2002), to determine whether the hydrocarbons released into the water column as a consequence of the spill were accumulated by the planktonic communities during the subsequent spring and early summer blooms. Surface sediments were also collected to assess the presence of the spilled oil, removed from the water column by downward particle transport. Plankton concentrations of PAHs (Sigma14 parent components) were in the range of 25-898 ng g(-1)dw, the highest values being close to coastal urban areas. However, the individual distributions were highly dominated by alkyl naphthalenes and phenanthrenes, paralleling those in the water dissolved fraction. The detailed study of petrogenic molecular markers (e.g. steranes and triterpanes, and methyl phenanthrenes and dibenzothiophenes) showed the occurrence of background petrogenic pollution but not related with the Prestige oil, with the possible exception of the station off Costa da Morte in May 2003, heavily oiled after the accident. The dominant northerly wind conditions during the spring and early summer 2003, which prevented the arrival of fresh oil spilled from the wreck, together with the heavy nature of the fuel oil, which was barely dispersed in seawater, and the large variability of planktonic cycles, could be the factors hiding the acute accumulation of the spilled hydrocarbons. Then, with the above exception, the concentrations of PAHs found in the collected samples, mostly deriving from chronic pollution, can be considered as the reference values for the region.

Animals↗
PubMed2004

Use of heterotrophic CO2 assimilation as a measure of metabolic activity in planktonic and sessile bacteria.

We have examined whether assimilation of CO2 can be used as a measure of metabolic activity in planktonic and sessile heterotrophic bacteria. CO2 assimilation by environmental samples and pure cultures of heterotrophic bacteria was studied using 14CO2 and 13CO2 as tracers. Heterotrophic growth on complex organic substrates resulted in assimilation of CO2 into cell biomass by activated sludge, drinking water biofilm, and pure cultures of Escherichia coli ATCC 25922, Es. coli ATCC 13706, Rhodococcus ruber, Burkholderia sp., Bacillus circulans, Pseudomonas putida, Pseudomonas stutzeri, and Pseudomonas aeruginosa. Analysis of 13C-labelled phospholipid fatty acids (PLFAs) confirmed that heterotrophic bacteria may assimilate 13CO2 into cell macromolecules such as membrane lipids. All major PLFAs extracted from activated sludge and drinking water biofilm samples were enriched in 13C after incubation with CO2. Between 1.4% and 6.5% of the biomass produced by cultures of P. putida and a drinking water biofilm during growth in complex media was apparently derived from assimilation of CO2. Resting cells assimilated less CO2 compared to actively growing cells, and CO2 assimilation activity correlated with the amount of biomass produced during heterotrophic growth. The 14CO2 assimilation assay was evaluated as a tool to examine inhibitory effects of biocides on planktonic and sessile heterotrophs (biofilms). On the basis of 14CO2 assimilation activity, the minimum inhibitory concentration (MIC) of benzalkonium chloride was estimated to 21.1 and 127.2 mg l(-1) for planktonic and biofilm samples, respectively. The results indicate that assimilation of isotopically labelled CO2 can be used as a relatively simple measure of metabolic activity in heterotrophic bacteria. CO2 assimilation assays may be used to study the effects of antimicrobial agents on growth and survival of planktonic and sessile heterotrophic organisms.

Anti-Bacterial Agents↗
PubMed2005

Detection and differentiation of Vibrio vulnificus in seawater and plankton of a coastal zone of the Mediterranean Sea.

Vibrio vulnificus, a human and animal pathogen, is present in low numbers in the Mediterranean Sea. Seawater and plankton samples were collected from a marine coastal zone of the Straits of Messina in the Mediterranean Sea (Italy) in order to investigate V. vulnificus as free-living (>0.2 microm) and associated with small (>64 microm) and large plankton (>200 microm) utilizing cultural and molecular techniques. Characteristic colonies, grown on thiosulfate, citrate, bile salts and sucrose agar plates, were identified using a biochemical protocol system. A PCR assay was used to confirm isolates and to directly detect V. vulnificus in environmental concentrated samples. Specific primers were used to target the structural cytotoxin/hemolysin gene and the variable regions of 16S rRNA species-specific for V. vulnificus. In addition, a tri-primer PCR of 16S rRNA was used for the differentiation of V. vulnificus strains. Direct detection in marine samples was more frequent than isolation of culturable forms. All isolates were assigned to V. vulnificus biotype 1, 16S rRNA type B. These results confirm the low incidence of V. vulnificus in Mediterranean coastal waters. The isolation of cultivable forms is limited to the warmest months. 16S rRNA primers were the most sensitive molecular tool as they allowed detection of V. vulnificus in 79.1% of samples. Due to the low incidence of V. vulnificus in the Mediterranean coastal environment, its detection requires a molecular approach. The occurrence of V. vulnificus as plankton-associated confirms the role of plankton as a potential reservoir for this pathogen.

Bacterial Proteins↗
PubMed2003

Plankton blooms induced by turbulent flows.

Plankton play an important role in the ecology of the ocean and the climate because of their participation in the global carbon cycle at the base of the food chain. However, damaging plankton blooms can sometimes occur and are initially characterized by sudden transient increases in the phytoplankton population. They are thought to be driven by several effects, such as seasonal variations in temperature and salinity, and nutrient mixing. Furthermore, phytoplankton and zooplankton have different buoyancy properties, leading to a differential response in turbulent environments. In this paper, we investigate this effect in a model of advected plankton dynamics. We find that, over a range of parameter values, flows of marine species subjected to inertial/viscous forces naturally lead to patchiness and, in turn, periodically sustained plankton blooms.

Animals↗
PubMed2006

Candida albicans SNO1 and SNZ1 expressed in stationary-phase planktonic yeast cells and base of biofilm.

The Candida albicans homologues of the most studied Saccharomyces cerevisiae stationary-phase genes, SNO1 and SNZ1, were used to test the hypothesis that, within a biofilm, some cells reach stationary phase within continuously fed, as well as static, C. albicans biofilms grown on dental acrylic. The authors first studied the expression patterns of these two genes in planktonic growth conditions. Using real-time RT-PCR (RT-RTPCR), increased peak expression of both SNZ1 and SNO1 was observed at 5 and 6 days, respectively, in C. albicans grown in suspension culture. SNZ1-yellow fluorescent protein (YFP) and SNO1-YFP were constructed to study expression at the cellular level and protein localization in C. albicans. Snz1p-YFP and Sno1p-YFP localized to the cytoplasm with maximum expression (>90 %) at 5 and 6 days, respectively, in planktonic conditions. When yeast growth was reinitiated, loss of fluorescence began immediately. Germ tubes and hyphae were non-fluorescent. Pseudohyphae began appearing at 9 days in planktonic yeast culture and expressed each protein by 11 days; however, the cells budding from pseudohyphae were not fluorescent. Biofilm was formed in vitro under either static or continuously fed conditions. Increased expression of the two genes was shown by RT-RTPCR, beginning by day 3 and increasing through to day 15 (continuously fed biofilm). Only the bottommost layer of acrylic-adhered cells in the biofilm showed 25 and 40 % fluorescence at 6 and 15 days, respectively. These observations suggest that only a few cells in C. albicans biofilms express genes associated with the planktonic stationary phase and that these are found at the bottom of the biofilm adhered to the surface.

Biofilms↗
PubMed2001

Patchy environment as a factor of complex plankton dynamics.

We study the role of the diffusive interaction in plankton dynamics in a patchy environment. We use a minimal reaction-diffusion model of the nutrient-plankton-fish food chain to simulate the diffusive interaction between fish-populated and fish-free habitats. We show that such interaction can give rise to spatiotemporal plankton patterns. The plankton dynamics depend on the fish predation rate and can exhibit both regular and chaotic behavior. We show that limit cycle and chaotic attractor coexist in the system. The entire basin of attraction of the limit cycles is found to be riddled with "holes" leading to the competitive chaotic attractors. The chaotic dynamics is typical of a wide range of the fish predation rates.

Animals↗