Relationship between bacterial counts and endotoxin concentrations in the air of wastewater treatment plants.

The relationship between bacterial counts and endotoxin concentrations in air samples was studied. Selective EMB medium favored the growth of a larger portion of airborne gram-negative bacteria than LES Endo or MacConkey medium and was a good predictor of the endotoxin levels determined with a chromogenic Limulus assay of the air of wastewater treatment plants. The bacterial counts determined with nonselective media correlated poorly with airborne endotoxin levels; however, R2A medium yielded higher viable bacterial counts than TYG medium. Direct counting by epifluorescence microscopy yielded the highest bacterial counts, but no correlation was obtained between total bacterial counts and endotoxin concentrations.     

Relationship between bacterial counts and endotoxin concentrations in the air of wastewater treatment plants.

The relationship between bacterial counts and endotoxin concentrations in air samples was studied. Selective EMB medium favored the growth of a larger portion of airborne gram-negative bacteria than LES Endo or MacConkey medium and was a good predictor of the endotoxin levels determined with a chromogenic Limulus assay of the air of wastewater treatment plants. The bacterial counts determined with nonselective media correlated poorly with airborne endotoxin levels; however, R2A medium yielded higher viable bacterial counts than TYG medium. Direct counting by epifluorescence microscopy yielded the highest bacterial counts, but no correlation was obtained between total bacterial counts and endotoxin concentrations.     

Evaluation of a radiometric method for studying bacterial activity in the presence of antimicrobial agents

In a study involving 2760 tests, the BACTEC semi-automatic radiometric method which measures bacterial metabolic activity and produces a BACTEC growth index, was compared with two conventional methods commonly used for determining growth, absorbance and viable counts. In 92% of radiometry tests the suppression of growth was inversely related to the antibiotic concentration. This compared with 83% for absorbance and 63% for viable counts. The radiometric method was found to be more rapid, easier to use and more reproducible in determining the effect of antibiotics on the activity of bacteria than viable counting or absorbance methods.     

A comparison of methods for assessing toxicant effects on algal growth

Summary Ankistrodesmus braunii was used as the test organism to assess the effects of mercuric chloride on the growth of this species. Optical density measurements correlated highly with dry weight determinations, chlorophyll content, total cell counts, and respiring cell counts. Any one of the above methods may be used alone or in combination with other methods to assess the effects of toxicants on algal growth and survival.     

极地雪藻在不同培养基中生长和虾青素累积的研究

在常温（23℃）和低温（10℃）条件下,用BBM、Bold 1NV、TAP和MCM四种培养基对极地雪藻进行培养。通过对生长速率、细胞数、A535值及虾青素累积量的测定,比较不同培养基、不同培养条件对极地雪藻的生长与虾青素累积的影响。结果表明,低温有利于极地雪藻的生长和虾青素的累积,BBM培养基比其它培养基更适合极地雪藻的生长,10℃时条件下其生长速率最高,培养14d细胞数可达到3．53×10^6／mL;在高光强条件下培养15d后用BBM培养基培养的极地雪藻细胞的虾青素累积为其它培养基的2．21-3．59倍。     

Analysis of variability in vertebral morphology and growth ring counts in two Carcharhinid sharks

Inter- and intra-regional variations in vertebrae morphology and growth increment counts (band counts) were analyzed for two carcharhinid shark species, Carcharhinus plumbeus (n = 10) and C. limbatus (n = 11). Five sequential vertebrae were removed from the cervical region, above the branchial chamber and posterior to the chondrocrainium, and thoracic region, below the first dorsal fin. Dorsal–ventral height, medial–lateral breadth, and caudal–cranial length were measured for each sampled vertebra. Results indicate no significant difference in vertebral morphology within a sampled region of the vertebral column. However, a significant difference in vertebral morphology was noted between regions for both shark species, with thoracic vertebrae consistently larger than cervical vertebrae. A sub-set of three vertebrae was taken from each sampled region of each shark for sectioning and counting of growth increments. Analyses of growth increment counts by two readers indicated no significant difference in band counts within and between sampled regions.     

A note on yeast growth in media used for the cultivation of lactobacilli

Yeast species found in mayonnaise-based salads are capable of growth in media used for the isolation of lactobacilli. Many counts of lactobacilli from such products may, therefore, inadvertently include counts of yeasts. A method is presented whereby the use of media with and without chloramphenicol makes it possible to deduce a differential count of bacteria. It was not possible to prevent yeast growth in de Man, Rogosa and Sharpe agar by the addition of cycloheximide since many isolates were resistant to it.     

Recovery of exponentially growing cultures of Klebsiella pneumoniae NCIB 418 after heat shocks

Exponentially growing cultures of Klebsiella pneumoniae were subjected to heat shocks in the superoptimal and supermaximal temperature ranges for growth on glucose in a defined mineral salts medium. Transitory changes in the specific growth rate constant during recovery were evident. The response was heat shock temperature and exposure time dependent. Cell viability determinations, based on colony counts, indicated complete recovery from heat treatments at superoptimal temperatures. In contrast, at supermaximal temperatures, discrepancies in colony counts on different agars were observed. The kinetic response of the specific growth rate constant after a heat shock at supermaximal temperatures is explained by segregation within the bacterial population     

Inhibitory effects of titanium (III) citrate on enumeration of bacteria from rumen contents.

Titanium citrate (TC) or L-cysteine-sodium sulfide was added as a reducing agent to buffers and agar media used for enumeration of bacteria from rumen contents of high-forage-fed steers. Approximately equal colony counts were found on TC and L-cysteine-sodium sulfide-reduced media with rumen contents taken 8 h postfeeding, when active bacterial growth was occurring. The colony counts on TC medium were only 56% of those with L-cysteine-sodium sulfide medium with rumen contents taken 1 h prefeeding when bacterial growth was minimal. When colonies from L-cysteine-sodium sulfide medium were transferred to TC medium and vice versa, almost all colonies grew. The data indicate that TC can be inhibitory to bacteria upon their initial isolation from natural habitats, particularly when growth rates are low in these habitats.     

Growth of legionella and other heterotrophic bacteria in a circulating cooling water system exposed to ultraviolet irradiation

The effect of ultraviolet irradiation on the growth and occurrence of legionella and other heterotrophic bacteria in a circulating cooling water system was studied. Water of the reservoir was circulated once in 28 h through a side-stream open channel u.v. radiator consisting of two lamps. Viable counts of legionellas and heterotrophic bacteria in water immediately after the u.v. treatment were 0—12 and 0·7—1·2% of those in the reservoir, respectively. U.v. irradiation increased the concentration of easily assimilable organic carbon. In the u.v. irradiated water samples incubated in the laboratory the viable counts of heterotrophic bacteria reached the counts in reservoir water within 5 d. The increase in viable counts was mainly due to reactivation of bacterialcells damaged by u.v. light, not because of bacterial multiplication. Despite u.v. irradiation the bacterial numbers in the reservoir water, including legionellas, did not decrease during the experimental period of 33 d. The main growth of bacteria in the reservoir occurred in biofilm and sediment, which were never exposed to u.v. irradiation.     

A note on the use of the Catalasemetre in assessing the quality of milk

The Catalasemetre, for assessing the quality of raw and pasteurized milk, has been studied. No correlation was found between catalase activity and bacterial counts for farm bulk tank milks within the range 5.2 ± 10²-5.4 ± 10⁵ cfu/ml. Similarly, no relation was observed between catalase activity and somatic cell counts of milk (range of counts from 0.08 to 3.5). However, the catalase activity and bacterial count of pasteurized milks which had been pre-incubated at 21.C for 25 h in the presence of crystal violet-penicillin-nisin to inhibit Gram-positive bacterial growth were significantly related. Thus, the use of this pre-incubation procedure coupled with the Catalasemetre to estimate bacterial growth, has potential in assessing the keeping quality of pasteurized milk samples within 25.5 h of production. Results on the thermostability of native milk catalase are also presented.     

LIVE/DEAD BacLight : application of a new rapid staining method for direct enumeration of viable and total bacteria in drinking water.

A rapid epifluorescence staining method using the LIVE/DEAD Bacterial Viability Kit (BacLight) was applied to estimate both viable and total counts of bacteria in drinking water. BacLight is composed of two nucleic acid-binding stains: SYTO 9 and propidium iodide. SYTO 9 penetrates all bacterial membranes and stains the cells green, while propidium iodide only penetrates cells with damaged membranes, and the combination of the two stains produces red fluorescing cells. Optimal incubation conditions were found to be 15 to 20 min, at room temperature in the dark. Total (red + green) and viable (green) cells can hence be counted simultaneously. Factors affecting the staining procedure were tested (addition of glutaraldehyde, staining time, chlorine impact). In the absence of stress, BacLight viable counts were comparable and to 5-cyano-2,3-ditolyl tetrazolium (CTC) counts. BacLight total counts were comparable to acridine orange counts (differing by <0.1 log/ml). However, the increase in environmental stresses (chlorine, growth rate or temperature) induced a decrease in viability that was more pronounced for CTC and plate counts than for BacLight viable counts.     

混合培养对固氮菌和纤维素分解菌生长及固氮的影响

对筛选的自生固氮菌和纤维素分解菌进行混合培养 ,研究了菌数与菌液含氮量的变化情况 ,并与其单独培养进行了比较。实验证明 :在混合培养条件下 ,两种菌能相互利用、相互促进 ,混合培养液的菌数增加 ,固氮菌的固氮能力提高。这两种菌可混合培养制成混合菌剂。。     

Use of the Malthus conductance growth analyser to determine numbers of thermophilic streptococci on stainless steel

The use of the Malthus conductance growth analyser for the detection of Streptococcus bovis attached to stainless steel surfaces was evaluated. A comparison between the results from acridine orange epifluorescence direct counts, swab recovery viable count and conductance estimates of attached cell concentrations, based on calibrations for planktonic cells, showed that the conductance results were up to 2 log₁₀ greater than the epifluorescence results and the swab counts. The growth rates of planktonic and attached cells were similar over 16 h using the Malthus technique. This suggests that the Malthus technique detects more attached cells of Strep. bovis than epifluorescence microscopy or swab recovery.     

Historical versus Contemporary Climate Forcing on the Annual Nesting Variability of Loggerhead Sea Turtles in the Northwest Atlantic Ocean

A recent analysis suggested that historical climate forcing on the oceanic habitat of neonate sea turtles explained two-thirds of interannual variability in contemporary loggerhead (Caretta caretta) sea turtle nest counts in Florida, where nearly 90% of all nesting by this species in the Northwest Atlantic Ocean occurs. Here, we show that associations between annual nest counts and climate conditions decades prior to nest counts and those conditions one year prior to nest counts were not significantly different. Examination of annual nest count and climate data revealed that statistical artifacts influenced the reported 31-year lag association with nest counts. The projected importance of age 31 neophytes to annual nest counts between 2020 and 2043 was modeled using observed nest counts between 1989 and 2012. Assuming consistent survival rates among cohorts for a 5% population growth trajectory and that one third of the mature female population nests annually, the 41% decline in annual nest counts observed during 1998–2007 was not projected for 2029–2038. This finding suggests that annual nest count trends are more influenced by remigrants than neophytes. Projections under the 5% population growth scenario also suggest that the Peninsular Recovery Unit could attain the demographic recovery criteria of 106,100 annual nests by 2027 if nest counts in 2019 are at least comparable to 2012. Because the first year of life represents only 4% of the time elapsed through age 31, cumulative survival at sea across decades explains most cohort variability, and thus, remigrant population size. Pursuant to the U.S. Endangered Species Act, staggered implementation of protection measures for all loggerhead life stages has taken place since the 1970s. We suggest that the 1998–2007 nesting decline represented a lagged perturbation response to historical anthropogenic impacts, and that subsequent nest count increases since 2008 reflect a potential recovery response.     

Statistical evaluation of electronic and plate counts for estimating bacterial populations

Bacteria from cultures of Staphylococcus aureus, Pseudomonas geniculata, and Rhodotorula glutenis were counted by use of an electronic counter and by plate counts from broth cultures at selected periods from 0 to 24 hr. Variations in the two methods were noted, and the results were compared after calculating correlations, coefficients of variation, and nested analyses of variance. It was not possible to determine the absolute accuracy of the two methods; however, the precision of the results obtained with an electronic counter was better than that obtained with plate counting. It appears that electronic counting, because of ease and convenience, provides better comparative counts at a particular stage of growth, especially during the early stages of the growth period, whereas plate counting yields the best results in determining growth curves.     

Enumeration of Viable Bacteria in the Marine Pelagic Environment

The low percentage of living bacteria commonly obtained when comparing viable counts with total direct counts in seawater could be due more to inappropriate techniques for appreciating the growth ability of living cells than to unadapted culture conditions. The most-probable-number counts in filtered seawater cultures and the microscopic counts of 4(prm1),6-diamidino-2-phenylindole (DAPI)-stained aggregate-forming units grown on black polycarbonate filters appeared significantly correlated to the direct counts. Both these techniques show that in the superficial and intermediate water masses, the living cells may constitute an important (frequently higher than 20%) but highly variable part of the total populations. These viable counts appear more realistic than the conventional CFU counts, which provide only 0.001 to 0.2% of the total counts.     

Gastrointestinal health effects associated with the consumption of drinking water produced by point-of-use domestic reverse-osmosis filtration units

During a prospective epidemiological study of gastrointestinal health effects associated with the consumption of drinking water produced by reverse-osmosis domestic units, a correlation was demonstrated between the bacterial counts on R2A medium incubated at 35 degrees C and the reported gastrointestinal symptoms in families who used these units. A univariate correlation was found with bacterial counts on R2A medium at 20 degrees C but was confounded by the bacterial counts at 35 degrees C. Other variables, such as family size and amount of water consumed, were not independently explanatory of the rate of illness. These observations raise concerns for the possibility of increased disease associated with certain point-of-use treatment devices for domestic use when high levels of bacterial growth occur.     

THE ESTIMATION OF SULPHATE-REDUCING BACTERIA (D. DESULPHURICANS)

SUMMARY: Sodium sulphide or cysteine stimulated the growth of sulphate-reducing bacteria; small populations often did not grow without such supplements. Ascorbic acid, glutathione or thiolacetic acid had similar properties but thiolacetic acid was sometimes inhibitory, Dilution counts in liquid media or colony counts in agar media did not bear any regular relation to the total count unless one of these supplements was present. With suitable precautions colony counts reaching 50 to 60% of the total count were obtained in media incorporating cysteine and a ferrous salt (as an indicator of sulphide formation).
Samples of natural origin containing sulphate-reducing bacteria gave greater viable counts in cysteine-iron media than in unsupplemented media. Blackend culture tubes with natural populations were sometimes due to cysteine-decomposing organisms; further examination of positive tubes was therefore necessary.     

Determination of the growth curves of the mycelial and yeast forms of Paracoccidioides brasiliensis

Summary The growth curves of 2 different strains ofP. brasiliensis were determined. Cultures were made in a dialyzed trypticase soy broth and the growth assesed at selected intervals by means of viable cell counts. In the yeast form, both strains exhibited an uniform pattern of growth; the mycelial forms were also similar although one of the strains survived for a longer period of time. When the 2 yeast curves were compared with the mycelial ones, large differences were noticed. Thus, the mean survival time for the yeasts was 13.5 days while it was 50.25 days for the mycelia. During the exponential phase, the mean rate of growth was accelerated for the yeasts (0.110) in comparison with the one exhibited by the mycelia (0.0265).Irrespective of the form of growth and for both strains, death occurred abruptly, a few hours after a period when colony counts were high, indicating that the fungus was viable at the preceeding interval.This paper includes, in part, a thesis submitted by M. Arango to the University of Antioquia, Medellín, in fulfillment of the requirements for the Master of Science degree.