Distinct function of Pseudomonas aeruginosa type IV pili disclosed in the bacterial pass-through of membrane filter with smaller pore sizes

Membrane filter pass-through ability of Pseudomonas aeruginosa was analyzed with isogenic mutants. A flagellum-deficient fliC mutant required two-times longer time (12 hr) to pass through a 0.45-microm pore size filter. With 0.3- and 0.22-microm filters, however, the fliC mutant showed no remarkable disability. Meanwhile a pilA mutant defective in twitching motility failed to pass through the 0.22-microm filter. Complementation of the mutant with pilA gene on a plasmid restored the twitching motility and the 0.22-microm filter pass-through activity. Thus, the distinctive role of P. aeruginosa type IV pili in infiltration into finer reticulate structures was indicated.     

Membrane Filtration of the Reiter Treponeme

A membrane filtration technique with commercially available membrane filters (Millipore Corp.) was effective for the removal of Reiter treponemes from liquids such as fluorescent-antibody conjugates, to which the organisms are added for adsorption. Reiter treponemes from an 8-day culture were not microscopically detectable in filtrates through membranes with a pore diameter of 0.45 μm, but treponemes were demonstrated in the filtrate by cultural methods. No organisms of the 8-day culture passed through a membrane filter having a pore size of 0.22 μm, as determined by microscopy and culture. Culture data indicated that a filter with a pore size of 0.1 μm was necessary to prevent passage of treponemes from 4-day cultures. It is recommended that a membrane filter with a pore size of 0.22 μm or smaller be used for the removal of Reiter treponemes from suspensions and that the age of the culture be considered in choosing filter pore size.     

Enumeration of iron-oxidizing bacteria by the membrane filter technique

This work presents a simple methodology to enumerate ferrous-iron-oxidizing bacteria in solution, easily applicable in bioleaching industrial plants, because it does not require expertise or specific equipment. The enumeration is based on bacterial concentration by microfiltration through a membrane filter. The filter containing the bacteria is placed on an agarose plate containing ferrous sulphate for bacterial growth. No difference was observed for the enumeration of Acidithiobacillus ferrooxidans ATCC 19859 when either 0.1 or 0.22 m pore size membrane filters were used. However, when the technique was applied to bacteria present in pregnant leaching solution, the smaller bacteria present in these solutions passed through the 0.22 m pore size membrane. Therefore the number of bacteria could be underestimated if they are monitored and filtered using a filter with pore size greater than 0.1 m. The limit of detection of this technique was one ferrous-iron-oxidizing bacterium in the filtered solutions.     

Passage of Treponema pallidum Through Membrane Filters of Various Pore Sizes

The passage of Treponema pallidum through commercially available Millipore membrane filters of various pore sizes was examined. No microscopically detectable organisms passed through a filter with a pore diameter of 0.22 mum. As pore size was increased, progressively more organisms passed through. Motile organisms passed through filters to a greater extent than nonmotile ones; however, 22% of the motile and 50% of the nonmotile T. pallidum organisms did not pass through the largest pore diameter tested (14.0 mum). Filtration of T. pallidum suspensions through membrane filters may offer a way of separating the organisms from larger particles of debris which accompany their extraction from rabbit testicular syphilomas.     

Factors Influencing the Ability of Listeria monocytogenes To Pass through a Membrane Filter by Active Infiltration

Listeria monocytogenes infiltrated the reticulate structure of a membrane filter and passed through a filter with pore sizes of 0.45 μm and 0.2 μm in 6 to 24 h and 5 to 6 days, respectively. Flagellar motility and expansive pressure generated by the growing bacterial population were indicated as the driving forces of infiltration.     

Factors influencing the ability of Listeria monocytogenes to pass through a membrane filter by active infiltration

Listeria monocytogenes infiltrated the reticulate structure of a membrane filter and passed through a filter with pore sizes of 0.45 microm and 0.2 microm in 6 to 24 h and 5 to 6 days, respectively. Flagellar motility and expansive pressure generated by the growing bacterial population were indicated as the driving forces of infiltration.     

Degradation of arsenobetaine to inorganic arsenic by bacteria in seawater

The substances suspended in seawater were fractionated by membrane filtration into three fractions. Fraction 1 was collected on a membrane filter of 0.22 µm pore-size, fraction 2 on a 5 µm pore-size and fraction 3 on 0.22 µm pore-size from the filtrate passed through the 5 µm membrane filter. Arsenobetaine was incubated with each of these fractions in two media (ZoBell 2216E and a solution of inorganic salts) at 25 °C in the dark under aerobic conditions. The mixture added with fraction 3 was considered to contain only bacteria. In every case, in the inorganic salt medium, inorganic arsenic(V) was derived from arsenobetaine via trimethylarsine oxide. In the ZoBell medium, arsenobetaine was not degraded to inorganic arsenic, although trimethylarsine oxide was derived in every case. We conclude that the degradation of arsenobetaine to trimethylarsine oxide or inorganic arsenic can be accomplished in seawater by bacteria alone.     

Use of the 0.22 {micro}m Millipore membrane for light-transmission measurements of aquatic particles

The use of the 0.22 µm Millipore cellulose membrane forthe measurement of the in vivo absorption of aquatic particlesby the light-transmission method has been explored relativeto the performance of the currently used 0.7 µm WhatmanGF/F glass-fiber filter. The standard solvent extraction processfor pigment removal has been replaced by a newly developed processbased on NaClO bleaching. The tests carried out indicate thatthe two filters exhibit comparable performances. It has beenshown that a double measurement, performed first in the particlesretained in the GF/F filter and then on the sample obtainedpassing the GF/F filtrate through a Millipore membrane, allowsfor the selective determination of the absorption of the particlefraction with diameter in the 0.22–0.7 µm range.     

Studies on the Minimum Reproducible Unit of Staphylococcal L-Forms

The minimum size of a reproducible unit of staphylococcal L-forms was determined by filtration and electron microscopic methods. Ultrathin sections of an induced strain of Staphylococcal L-forms (STA-EMT-1) in liquid medium revealed several types of structures, all of which were bound by a single membrane and most of which possessed ribosome-like granules. Many of the small granules were less than 0.3 μm and were attached to the membrane of the large bodies. Using a serial filtration method, it was observed that viable L-forms were still detected in 0.22 μm filtrate, but the viable cell count of L-forms decreased in number with the decrease in pore size of membrane filters. A fractionation technique, using L-forms filtered through a membrane filter with a 0.45 μm pore size, revealed that there were three classes of small bodies but only the first class with ribosome-like granules over approximately 0.2 μm in diameter seems to be able to reproduce.     

Effect or preliminary filtration on the functional characteristics of bacterioplankton from Lake Khanka]

The dependence of the functional characteristics of bacterioplankton from the loess of Lake Khanka on the pore size of filtering materials was investigated. Soluble organic matter (SOM), bacteria, and bacterial consumers adsorbed on particles suspended in the lake water were found to filter differently depending on the pore size of the filtering material. Filters with pore size 4.5 microns (filters II) retained up to 20% of SOM and 20-30% of bacterial cells. Filters III with pore size 2.87 microns retained almost 50% SOM and about 40% of bacteria. The double layer of gauze no. 72 (referred to as filter I) with pores size 40 microns was unable to completely retain bacterial consumers. In the case of filtrates I and II, the generation time of bacterioplankton decreased with its increasing average daily concentration. In the case of filtrate III, the generation time of bacterioplankton was minimum and did not depend on its concentration. Oxygen consumption rates per one bacterial cell and per unit biomass in filtrates increased with decreasing pore size of the filters through which they had passed. The bacterial biomass and oxygen consumption rate increased exponentially in filtrates III and logarithmically in filtrates I.     

Effect of Preliminary Filtration on the Functional Characteristics of Bacterioplankton from Lake Khanka

The dependence of the functional characteristics of bacterioplankton from the loess of Lake Khanka on the pore size of filtering materials was investigated. Soluble organic matter (SOM), bacteria, and bacterial consumers adsorbed on particles suspended in the lake water were found to filter differently depending on the pore size of the filtering material. Filters with pore size 4.5 m (filters II) retained up to 20% of SOM and 20–30% of bacterial cells. Filters III with pore size 2.87 m retained almost 50% of SOM and about 40% of bacteria. The double layer of gauze no. 72 (referred to as filter I) with pores size 40 m was unable to completely retain bacterial consumers. In the case of filtrates I and II, the generation time of bacterioplankton decreased with its increasing average daily concentration. In the case of filtrate III, the generation time of bacterioplankton was minimum and did not depend on its concentration. Oxygen consumption rates per one bacterial cell and per unit biomass in filtrates increased with decreasing pore size of the filters through which they had passed. The bacterial biomass and oxygen consumption rate increased exponentially in filtrates III and logarithmically in filtrates I.     

Mortality in adult tsetse, Glossina morsitans morsitans, caused by entomopathogenic bacteria

Mortality in adult tsetse, Glossina morsitans morsitans, caused by Pseudomonas aeruginosa, Serratia marcescens, Bacillus sphaericus, Bacillus cereus, Bacillus thuringiensis H-14, B. thuringiensis 1, B. thuringiensis 5, B. thuringiensis var. insraelensis, and Providentia rettgeri was determined. When bacteria were smeared on rabbit skin and tsetse allowed to feed only once on the contaminated area, mortality 8 days postingestion was significantly higher (P less than 0.01) in tsetse fed on P. aeruginosa, S. marcescens, B. thuringiensis 1, and P. rettgeri and increased when tsetse were allowed to feed for the second time on the contaminated skin. With this smear technique, however, mortalities were generally not remarkable. In artificial membrane feeding experiments using low concentrations of bacteria (-10(6)/ml of blood), the B. thuringiensis strains caused low mortality, except B. thuringiensis H-14, which caused 59% mortality. However, at this concentration, P. aeruginosa, S. marcescens, B. cereus, and P. rettgeri caused highly significant (P less than 0.01) mortality (64-96%). When higher concentrations of bacteria (10(7)/ml) were used, all the bacteria tested, except B. sphaericus, caused high mortality ranging from 70 to 98%. Thus, mortality depended on the species of bacteria, the dose ingested, and time postingestion.     

Proteobacteria and Bacteroidetes are major phyla of filterable bacteria passing through 0.22 μm pore size membrane filter,in Lake Sanaru,Hamamatsu, Japan

141 filterable bacteria that passed through a 0.22 μm pore size filter were isolated from Lake Sanaru in Hamamatsu, Japan. These belonged to Proteobacteria, Bacteroidetes, Firmicutes, or Actinobacteria among which the first two phyla comprised the majority of the isolates. 48 isolates (12 taxa) are candidates assignable to new bacterial species or genera of Proteobacteria or Bacteroidetes.     

A membrane filter procedure for assaying cytotoxic activity in heterotrophic bacteria isolated from drinking water

Cytotoxic activity assays of Gram-negative, heterotrophic bacteria are often laborious and time consuming. The objective of this study was to develop in situ procedures for testing potential cytotoxic activities of heterotrophic bacteria isolated from drinking water systems. Water samples were passed through 0·45 μm membrane filters which were then placed upon appropriate media and incubated. After incubation, each membrane filter was transferred to the surface of Y-1 mouse adrenal cells overlaid with 1% agar. The filters were removed after exposure for 15 min. The Y-1 cells were then incubated at 37°C in 2·5% CO₂ for an additional 24 h. The release of putative cytotoxic and cytotonic products from the bacterial colonies was recognized by zones of cellular lysis and injury of Y-1 cells that appeared immediately beneath the membrane. Cytotoxic strains of Aeromonas, Vibrio, Escherichia , and Legionella spp. were readily recognized by this method. About 1% of the bacteria isolated from drinking water also released cytotoxic products. This frequency was dependent upon the primary medium used and the density of bacteria present. The majority of cytotoxic strains isolated from drinking water also expressed protease activity (95%) and haemolytic activity (70%). This in situ membrane filter procedure is a facile method for simultaneously testing many different bacterial colonies.     

Contamination of Bacteriological Media by Leptospira biflexa

Contamination of media with a strain of Leptospira biflexa was traced to the deionized water supply. The leptospiral contaminant appeared in media sterilized by filtration through 0.45- and 0.22-mum pore size membrane filters.     

Adherence of bacteria, yeast, blood cells, and latex spheres to large-porosity membrane filters.

Strong adherence of bacteria, yeast, erythrocytes, leukocytes, platelets, spores, and polystyrene spheres to membrane filter materials was noted during filtration through membranes with pore size diameters much larger than the particles themselves. Quantitative recovery on the membrane filters of these particles from low-concentration suspensions was achieved during gravity- or vacuum-assisted filtration through membranes with pore diameters as much as 30 times that of the filtered particles. Mechanical sieving was not responsible. The phenomenon was judged to be electrostatic. It could be partially blocked by pretreating the filter with a nonionic surfactant (Tween 20), and elution of adherent particles was achieved with 0.05% Tween 20. Gram-positive cocci were removed from suspension more efficiently than gram-negative rods. The commonly used cellulose membranes adsorbed more bacteria, blood cells, and other particles than did polycarbonate filters. Of lesser adsorptive capacity were vinyl acetate, nylon, acrylic, and Teflon membranes. Backwashing with saline, serum, 6% NaCl, dextran solutions, or phosphate buffers of varying molality and pH removed only a fraction of adherent particles. Tween 20 (0.05%) eluted up to 45% of adherent particles in a single back-filtration. Selected filters quantitatively removed the particles tested, which then could be washed and subjected to reagents for a variety of purposes. It is important to anticipate the removal of particles during membrane filtration, since it is not a simple mechanical event.     

A membrane filter procedure for assaying cytotoxic activity in heterotrophic bacteria isolated from drinking water

Cytotoxic activity assays of Gram-negative, heterotrophic bacteria are often laborious and time consuming. The objective of this study was to develop in situ procedures for testing potential cytotoxic activities of heterotrophic bacteria isolated from drinking water systems. Water samples were passed through 0.45 microns membrane filters which were then placed upon appropriate media incubated. After incubation, each membrane filter was transferred to the surface of Y-1 mouse adrenal cells overlaid with 1% agar. The filters were removed after exposure for 15 min. The Y-1 cells were then incubated at 37 degrees C in 2.5% CO2 for an additional 24 h. The release of putative cytotoxic and cytotonic products from the bacterial colonies was recognized by zones of cellular lysis and injury of Y-1 cells that appeared immediately beneath the membrane. Cytotoxic strains of Aeromonas, Vibrio, Escherichia, and Legionella spp. were readily recognized by this method. About 1% of the bacteria isolated from drinking water also released cytotoxic products. This frequency was dependent upon the primary medium used and the density of bacteria present. The majority of cytotoxic strains isolated from drinking water also expressed protease activity (95%) and haemolytic activity (70%). This in situ membrane filter procedure is a facile method for simultaneously testing many different bacterial colonies.     

Purification of Chlamydia trachomatis by a simple and rapid filtration method

A simple method for filter purification of Chlamydia trachomatis from cell culture is described. Crude homogenates of chlamydiae-infected cells were passed through a glass prefilter and a 0.6 microns pore diameter polycarbonate filter. The filtrate was then passed through a 0.2 microns pore diameter filter on which the chlamydiae were trapped. This filter was then back-washed to collect the organisms. These procedures removed cell debris and soluble protein, and yielded particles with a narrow size distribution. The mean yield of viable chlamydiae purified by filtration was 64% when the filters were washed at each stage of the process.     

The effect of filtration method on the efficiency of environmental DNA capture and quantification via metabarcoding

Environmental DNA (eDNA) is a promising tool for rapid and noninvasive biodiversity monitoring. eDNA density is low in environmental samples, and a capture method, such as filtration, is often required to concentrate eDNA for downstream analyses. In this study, six treatments, with differing filter types and pore sizes for eDNA capture, were compared for their efficiency and accuracy to assess fish community structure with known fish abundance and biomass via eDNA metabarcoding. Our results showed that different filters (with the exception of 20‐μm large‐pore filters) were broadly consistent in their DNA capture ability. The 0.45‐μm filters performed the best in terms of total DNA yield, probability of species detection, repeatability within pond and consistency between ponds. However performance of 0.45‐μm filters was only marginally better than for 0.8‐μm filters, while filtration time was significantly longer. Given this trade‐off, the 0.8‐μm filter is the optimal pore size of membrane filter for turbid, eutrophic and high fish density ponds analysed here. The 0.45‐μm Sterivex enclosed filters performed reasonably well and are suitable in situations where on‐site filtration is required. Finally, prefilters are applied only if absolutely essential for reducing the filtration time or increasing the throughput volume of the capture filters. In summary, we found encouraging similarity in the results obtained from different filtration methods, but the optimal pore size of filter or filter type might strongly depend on the water type under study.     

Na, k, and nonspecific solute requirements for induction and function of galactose active transport in an antarctic psychrophilic marine bacterium

Strong adherence of bacteria, yeast, erythrocytes, leukocytes, platelets, spores, and polystyrene spheres to membrane filter materials was noted during filtration through membranes with pore size diameters much larger than the particles themselves. Quantitative recovery on the membrane filters of these particles from low-concentration suspensions was achieved during gravity- or vacuum-assisted filtration through membranes with pore diameters as much as 30 times that of the filtered particles. Mechanical sieving was not responsible. The phenomenon was judged to be electrostatic. It could be partially blocked by pretreating the filter with a nonionic surfactant (Tween 20), and elution of adherent particles was achieved with 0.05% Tween 20. Gram-positive cocci were removed from suspension more efficiently than gram-negative rods. The commonly used cellulose membranes adsorbed more bacteria, blood cells, and other particles than did polycarbonate filters. Of lesser adsorptive capacity were vinyl acetate, nylon, acrylic, and Teflon membranes. Backwashing with saline, serum, 6% NaCl, dextran solutions, or phosphate buffers of varying molality and pH removed only a fraction of adherent particles. Tween 20 (0.05%) eluted up to 45% of adherent particles in a single back-filtration. Selected filters quantitatively removed the particles tested, which then could be washed and subjected to reagents for a variety of purposes. It is important to anticipate the removal of particles during membrane filtration, since it is not a simple mechanical event.