Survival of Candida albicans in tropical marine and fresh waters

A survey of Candida albicans indicated that the organism was present at all sites sampled in a rain forest stream and in near-shore coastal waters of Puerto Rico. In the rain forest watershed no relationship existed between densities of fecal coliforms and densities of C. albicans. At two pristine sites in the rain forest watershed both C. albicans and Escherichia coli survived in diffusion chambers for extended periods of time. In near-shore coastal waters C. albicans and E. coli survival times in diffusion chambers were enhanced by effluent from a rum distillery. The rum distillery effluent had a greater effect on E. coli than on C. albicans survival in the diffusion chambers. These studies show that neither E. coli nor C. albicans organisms are good indicators of recent fecal contamination in tropical waters. It further demonstrates that pristine freshwater environments and marine waters receiving organic loading in the tropics can support densities of C. albicans which may be a health hazard.     

Species richness in tropical fresh waters of Australia

General ecological expectations about the relationship between latitude and species richness are that at low latitudes (the tropics) species richness is greater than at higher latitudes (temperate and polar regions). Recent work suggests that this may not be the case for several habitat types and biological groups in Australia. Results are conflicting: on present evidence (admittedly sparse) it appears that in Australian tropical fresh waters species richness is generally depressed in zooplankton and littoral microfaunal communities, but not in macroinvertebrate communities in typical streams and in fish communities (and perhaps also in amphibian and reptile communities). The situation is indeterminate for tropical phytoplankton and macrophyte communities.     

Photosynthetic rates in four tropical African fresh waters

SUMMARY. Seasonal changes in photosynthetic rates of phytoplankton and underwater light in four Kenyan fresh waters (Lake Naivasha, Crescent Island Crater, Oloidien Lake and Winam Gulf) were measured in 1973 and 1974. Daily variations in water temperature were only slightly less than seasonal changes, and complete vertical mixing usually occurred each day. Well oxygenated water from top to bottom provided evidence for daily mixing. The vertical profiles of photosynthetic rates in the four lakes had the familiar feature of subsurface maxima. Of the photosynthetically available radiation (PAR), 1% coincided with the limit of detection of photosynthesis in Naivasha and Crescent Island Crater. The PAR at the depth of the maximal photosynthetic rate was higher for Naivasha (mean= 1.71 einsteins (E) m^?2) than for the Oloidien and Crescent Island Crater (means = 1.23 and 1.20 E m^?2 h^?1, respectively). The maximal rates of photosynthesis (mg O2 m^?3 h^?1) were usually higher in Oloidien (260–750) and Winam Gulf (230–640) than in Naivasha (150–240) and were least in Crescent Island Crater (50–180). Chlorophyll-a concentrations were directly related to photosynthetic rates. Because of the inverse relation between euphotic zone depth and maximal photosynthetic rates, the areal rates varied less among the lakes than the volumetric rates (i.e. 3.0–12.1 g O2 m^?2 day^?1). The efficiency of utilization of PAR expressed on a molar basis ranged from 6.1 to 1.9 mmol O₂ E^?1, but was usually 2–4 mmol O₂ E^?1. The seasonal changes over a 12-month period in the areal photosynthetic rates ranged from a 3-fold variation in Oloidien and Crescent Island Crater to a 1.5-fold variation in Naivasha. In Winam Gulf over a 5-month period a 2.3-fold variation occurred.     

Sensitivity of Legionella pneumophila to sunlight in fresh and marine waters.

Studies were carried out to assess the sunlight sensitivity of Legionella pneumophila suspended in fresh and marine waters. Comparison studies on sunlight sensitivity of lake water bacteria, Pseudomonas aeruginosa, Escherichia coli and Streptococcus faecalis, were also undertaken. The effects of full sunlight and polyacrylic-screened sunlight were monitored in the study. Results indicate that L. pneumophila cells are slightly more sensitive to sunlight in seawater than in fresh water. Enumeration of sunlight-stressed bacteria in fresh water was found to be dependent on the medium used, and the following order of sensitivity to sunlight, from least to most sensitive, was noted: natural lake water bacteria, L. pneumophila, P. aeruginosa, E. coli, and S. faecalis.     

Adhesins in Candida albicans.

The adherent properties of Candida albicans blastoconidia and germ tubes have long been appreciated, but little is known about the mechanisms responsible for adherence. Recently, three genes, ALA1, ALS1 and HWP1, encoding proteins with adherent properties and motifs consistent with linkage to the beta-1, 6-glucan of C. albicans cell walls have provided insight into the topology of protein adhesins. Hwp1, a developmentally regulated adhesin of germ tubes and hyphae, attaches to buccal epithelial cells by an unconventional, transglutaminase-mediated mechanism of adhesion.     

Survey of human enterovirus occurrence in fresh and marine surface waters on Long Island.

A variety of surface water systems, including a lake, a creek, and two marine embayments, were analyzed on a monthly basis for indigenous human enteroviruses and coliform bacteria. Findings are discussed in terms of the probable pollution sources to each system and their relationship to data from previous studies.     

Survey of human enterovirus occurrence in fresh and marine surface waters on Long Island.

A variety of surface water systems, including a lake, a creek, and two marine embayments, were analyzed on a monthly basis for indigenous human enteroviruses and coliform bacteria. Findings are discussed in terms of the probable pollution sources to each system and their relationship to data from previous studies.     

Genetics of Candida albicans.

Candida albicans is among the most common fungal pathogens. Infections caused by C. albicans and other Candida species can be life threatening in individuals with impaired immune function. Genetic analysis of C. albicans pathogenesis is complicated by the diploid nature of the species and the absence of a known sexual cycle. Through a combination of parasexual techniques and molecular approaches, an effective genetic system has been developed. The close relationship of C. albicans to the more extensively studied Saccharomyces cerevisiae has been of great utility in the isolation of Candida genes and development of the C. albicans DNA transformation system. Molecular methods have been used for clarification of taxonomic relationships and more precise epidemiologic investigations. Analysis of the physical and genetic maps of C. albicans and the closely related Candida stellatoidea has provided much information on the highly fluid nature of the Candida genome. The genetic system is seeing increased application to biological questions such as drug resistance, virulence determinants, and the phenomenon of phenotypic variation. Although most molecular analysis to data has been with C. albicans, the same methodologies are proving highly effective with other Candida species.     

Effect of Relative Humidity on Survival of Candida albicans and Other Yeasts

Individual blastospores of Candida albicans were deposited on the surface of 50-mm membranes (Millipore Corp.) and placed within sealed glass chambers at various relative humidities (RH). After 48 hr, virtually all cells maintained at 100 and 10% RH had survived, but 84% of the cells maintained at 60% RH failed to develop into colonies when transferred to Sabouraud medium. No morphological abnormalities could be observed in cells surviving low RH values, but their initial rate of multiplication after transfer to Sabouraud medium was greatly reduced, compared to that demonstrated by cells maintained at 100% RH. At 60% RH, the exposure time required to kill 50% of the blastospores was 2 to 3.5 days. The inimical effect of 60% RH was confirmed in a total of 21 isolates of C. albicans. No deleterious effect was noted when 12 other species of yeasts were subjected to 10, 60, and 100% RH. The single isolate of Candida brumptii and 1 out of the 20 isolates of Cryptococcus neoformans tested also failed to grow after blastospores had been exposed to 60% RH for 4 days.     

Decay of sewage-associated bacterial communities in fresh and marine environmental waters and sediment

Applied Microbiology and Biotechnology - Understanding the microbial quality of recreational waters is critical to effectively managing human health risks. In recent years, the development of new...     

Genetics of Candida albicans.

Candida albicans is among the most common fungal pathogens. Infections caused by C. albicans and other Candida species can be life threatening in individuals with impaired immune function. Genetic analysis of C. albicans pathogenesis is complicated by the diploid nature of the species and the absence of a known sexual cycle. Through a combination of parasexual techniques and molecular approaches, an effective genetic system has been developed. The close relationship of C. albicans to the more extensively studied Saccharomyces cerevisiae has been of great utility in the isolation of Candida genes and development of the C. albicans DNA transformation system. Molecular methods have been used for clarification of taxonomic relationships and more precise epidemiologic investigations. Analysis of the physical and genetic maps of C. albicans and the closely related Candida stellatoidea has provided much information on the highly fluid nature of the Candida genome. The genetic system is seeing increased application to biological questions such as drug resistance, virulence determinants, and the phenomenon of phenotypic variation. Although most molecular analysis to data has been with C. albicans, the same methodologies are proving highly effective with other Candida species.     

Septal ultrastructure in Candida albicans.

Fine structural studies on the septa of Candida albicans in vitro (when leading a saprophytic existence) and the organism in its invasive form (as a pathogen in oral candidosis) have shown that in the former the septum exhibits a unique central perforation resembling an aggregate of fine canaliculi connecting one cell to the other. In the invasive form the septum is non-perforated and appears as a solid structure. Septal ultrastructure is well characterised in many pathogenic fungi. Our observations on Candida albicans do not resemble any previous studies carried out on other deutromycetous fungi.     

Peptide transport in Candida albicans.

The tripeptide L-methionyl-L-methionyl-L-[METHYL-14C]methionine was taken up into Candida albicans by a saturable system with a pH optimum of 3.5, a temperature optimum of 37 degrees C and an apparent Km of 3.3 x 10(-5) M. Metabolic inhibitors such as sodium azide and dinitrophenol completely prevented uptake. Neither methionine nor dimethionine effectively competed with trimethionine uptake. (Leu)3, Gly-Met-Gly, acetyl-(Met)3, D-Met-L-Met-L-Met and Met-Met-Ile effectively competed with (Met)3 uptake, whereas (Lys)3, L-Met-L-Met-D-Met, D-Met-D-Met-D-Met, (Met)3 methyl ester and (Ala)3 did not. Trimethionine was rapidly hydrolysed by a peptidase after entry into the cell.     

Phospholipase activity in Candida albicans.

Phospholipase A and lysophospholipase have been identified as the enzymes responsible for phospholipid hydrolysis by Candida albicans. The method used to identify and measure the activity of these enzymes is described, and the probable significance of phospholipase in the invasion of the epithelium by Candida albicans discussed.     

Natural heterozygosity in Candida albicans.

We subjected 16 Candida albicans clinical isolates to ultraviolet radiation and tested the survivors for auxotrophy. Six isolates displayed strongly biased auxotroph spectra: three yielded methionine auxotrophs, two yielded both isoleucine-valine and adenine auxotrophs, and one yielded lysine auxotrophs. We present evidence that auxotrophs arise by segregation from naturally occurring heterozygous states. The remaining isolates yielded few or no auxotrophs in an arbitrary sample (greater than 2,500) of survivors of irradiation. Our experiments indicate that C. albicans is diploid, although aneuploidy (2n + i) cannot be rigorously excluded. We discuss the possible utility of heterozygosity as a marker in epidemiological studies, and we discuss a rationale for the frequent occurrence of heterozygosity.     

Calcification by Candida albicans.

Candida albicans was grown in a chamically defined medium in which certain microorganisms are known to calcify. The fungus developed calcium phosphate deposits with the same X-ray diffraction maxima as biological apatite.     

Instability of Candida albicans hybrids.

Total cellular DNA content, determined by a colorimetric method, was used as an index of ploidy in Candida albicans. Mononucleate hybrids were formed by fusion of spheroplasts derived from diploid parent strains. Five hybrids, of six studied, were taken to be tetraploid on the basis of estimated DNA content. One hybrid was taken to be hexaploid or near-hexaploid. Selection for increased resistance to 5-fluorocytosine in the hybrids, which were heterozygous for resistance, resulted in isolation of variants which were of lower ploidy than the hybrids from which they originated. Variants were obtained which corresponded (in measured DNA content) to aneuploid, triploid, and diploid states. These results may form the basis of a cyclic parasexual system (2n X 2n----4n----2n) for genetic analysis of this asexual species.