Airborne Bacteria in an Urban Environment

Samples were taken at random intervals over a 2-year period from urban air and tested for viable bacteria. The number of bacteria in each sample was determined, and each organism isolated was identified by its morphological and biochemical characteristics. The number of bacteria found ranged from 0.013 to 1.88 organisms per liter of air sampled. Representatives of 19 different genera were found in 21 samples. The most frequently isolated organisms and their percent of occurence were Micrococcus (41%), Staphylococcus (11%), and Aerococcus (8%). The bacteria isolated were correlated with various weather and air pollution parameters using the Pearson product-moment correlation coefficient method. Statistically significant correlations were found between the number of viable bacteria isolated and the concentrations of nitric oxide (−0.45), nitrogen dioxide (+0.43), and suspended particulate pollutants (+0.56). Calculated individually, the total number of Micrococcus, Aerococcus, and Staphylococcus, number of rods, and number of cocci isolated showed negative correlations with nitric oxide and positive correlations with nitrogen dioxide and particulates. Statistically significant positive correlations were found between the total number of rods isolated and the concentration of nitrogen dioxide (+0.54) and the percent relative humidity (+0.43). The other parameters tested, sulfur dioxide, hydrocarbons, and temperature, showed no significant correlations.     

Microorganisms cultured from stratospheric air samples obtained at 41 km

Samples of air removed from the stratosphere, at an altitude of 41 km, were previously found to contain viable, but non-cultureable bacteria (cocci and rods). Here, we describe experiments aimed at growing these, together with any other organisms, present in these samples. Two bacteria (Bacillus simplex and Staphylococcus pasteuri) and a single fungus, Engyodontium album (Limber) de Hoog were isolated from the samples. Although the possibility of contamination can never be ruled out when space-derived samples are studied on earth, we are confident that the organisms originated from the stratosphere. Possible mechanisms by which these organisms could have attained such a height are discussed.     

Isolation of hexavalent chromium-reducing Cr-tolerant facultative anaerobes from tannery effluent

Several facultative anaerobes tolerant to high levels of chromate (>400 mg/ml) were isolated from tannery effluents. These isolates displayed varying degrees of Cr(VI) reduction under aerobic and anaerobic conditions at room temperature (24+/-2 degrees C). Interestingly, eight isolates were efficient in reducing 70% Cr(VI) anaerobically. This includes 5 isolates of genus Aerococcus, two isolates of Micrococcus and single isolate of genus Aeromonas. These isolates were subjected to further characterization for possible use in Cr(VI) detoxification of industrial wastes. This is the first report of Aerococcus sp. capable of Cr(VI) reduction >70% anaerobically. These bacteria were further checked for tolerance to a variety of other heavy metals. Our study indicates the possible use of these bacteria in environmental clean up.     

Microbial Progression in Sliced Vacuum Packaged Bacon at Refrigeration Temperatures

S ummary . Three hundred and forty eight strains of micro-organisms were isolated from packaged bacon which had been cured by one or other of 2 methods (A and B) and stored at 0–10° for 7 weeks. Before storage, Micrococcus sub-group 7 (47%) and coryneform bacteria (33%) were the principal contaminants of bacon cured by method A and Micrococcus subgroup 1 (20%) and Microbacterium thermosphactum (21%), in bacon cured by method B. After 7 days at 0°, coagulase negative staphylococci accounted for 10 and 33% of the microflora in bacon A and B, respectively: other organisms were micrococci, 60% (A) and 25% (B); corynebacteria, 20% (A) and 12·5% (B), yeasts ( Torulopsis candida and T. dattila ) 5% (A) and 29% (B). In the following month at 10°, Micrococcus sub-group 5 was the dominant (43–88%) contaminant of bacon B; the incidence of Streptococcus Group N ranged from 27–36% and that of unidentified lactic acid bacteria from 23–32%. Towards the end of storage, the order of dominance was Micrococcus sub-group 3 (38–58%) and atypical streptobacteria (38%) in A; Streptococcus Group N (42%) and Gram positive rods (5–20%) in B. Staphylococci tended to die out during storage of bacons cured by the 2 methods and coagulase positive staphylococci were not isolated.     

Ability of bacteria isolated from the hospital environment to proliferate in infusion fluids

The ability of some bacteria isolated from environmental sources to grow in commonly administered infusion fluids was investigated. Infusion fluids may become contaminated with bacteria present in the environment in which they are being administered and the ability of such bacteria to proliferate within commonly used infusion fluids is therefore clinically significant. Bacteria present in the air and sink drains in wards at the Ife State Hospital were isolated, identified, and comprised fifteen Gram-positive and five Gram-negative organisms. Fourteen of the organisms obtained were introduced into sterile distilled water and five different infusion fluid preparations and were monitored over a 48 h period. It was found that, in general, Gram-positive organisms did not grow in the fluids used, while Gram-negative organisms were able to proliferate in the same fluids. Some Gram-positive organisms showed remarkable ability to remain viable in infusion fluids for more than 48 h.     

Effects of nitric oxide and nitrogen dioxide on bacterial growth.

The effects of low concentrations of nitric oxide (NO) and nitrogen dioxide (NO2) on actively dividing cultures of Staphylococcus aureus, Micrococcus luteus, Micrococcus roseus, Serratia marcescens, Bacillus subtilis, Bacillus circulans, Bacillus megaterium, and Bacillus cereus were studied. Fresh cultures of each organism were incubated for 24 h at 25 degrees C on both nutrient agar and mineral salts glucose agar plates under atmospheres containing various low concentrations of NO in air (0 to 1.9 ppm [0 to 2.0 micrograms/g of air]), NO2 in air (0 to 5.5 ppm [0 to 8.8 micrograms/g of air]), or NO and NO2 in air. Bacteria grown under air only were used as controls. After incubation, the colonies that developed on the plates were counted. None of the bacteria tested was affected by NO or NO2 at the indicated concentrations while growing on nutrient agar. Serratia marcescens, B. circulans, B. subtilis, B. megaterium, and B. cereus grown on mineral salts glucose agar were not significantly affected by NO or NO2. Low concentrations (0 to 1.9 ppm) of NO were bacteriostatic to log-phase cultures of M. roseus, M. luteus, and Staphylococcus aureus grown on mineral salts glucose agar. Bacteriostatic activity over a 24-h interval was maximal at an initial NO concentration of 1 ppm. Appreciable amounts of NO2 were produced in 24 h at initial NO concentrations greater than 1 ppm. These results suggest that NO2 may reduce the bacteriostatic activity of NO. Low concentrations (0 to 5.5 ppm) of NO2 in air did not affect any of the bacteria tested. At these low concentrations, NO affected bacterial growth, although NO2, NO2-, and NO3- did not. In addition, it was determined that the bacteriostatic activity observed in this study was not due to an increase in the acidity of the medium.     

Effect of Packaging under Carbon Dioxide, Nitrogen or Air on the Microbial Flora of Pork Stored at 4°C

Changes in the microbial flora of pork packed in laminated plastic bags and stored at 4 °C were studied in an initial atmosphere of carbon dioxide, nitrogen or air. The time needed for the total aerobic count at 28 °C to reach 5 × 10⁶ organisms/cm² was about 7 times longer in carbon dioxide than in air, whilst in nitrogen it was about twice as long.
The predominant organisms on fresh pork taken directly from the processing line were: Acinetobacter calcoaceticus , non-fluorescent Pseudomonas spp. and Flavobacterium spp. After storage in air for 7 d, more than 90% of the flora consisted of non-fluorescent Pseudomonas spp. After storage in nitrogen for 10 d, 70% of the flora consisted of non-fluorescent Pseudomonas spp. with lower levels of fluorescent Pseudomonas spp., Kurthia zopfii, Aeromonas hydrophila and Lactobacillus plantarum. The non-fluorescent Pseudomonas spp. could be divided into three different groups, on proteolytic and lipolytic ability; the distribution of the groups was markedly different between pork loins stored in air and nitrogen.
On pork stored in carbon dioxide for 21 d the flora consisted of L. plantarum together with lower levels of heterofermentative lactic acid bacteria. When the storage time in carbon doxide was prolonged to 35 d, the proportion of heterofermentative lactic acid bacteria increased to about 50% of the flora.     

Effects of nitric oxide and nitrogen dioxide on bacterial growth

The effects of low concentrations of nitric oxide (NO) and nitrogen dioxide (NO2) on actively dividing cultures of Staphylococcus aureus, Micrococcus luteus, Micrococcus roseus, Serratia marcescens, Bacillus subtilis, Bacillus circulans, Bacillus megaterium, and Bacillus cereus were studied. Fresh cultures of each organism were incubated for 24 h at 25 degrees C on both nutrient agar and mineral salts glucose agar plates under atmospheres containing various low concentrations of NO in air (0 to 1.9 ppm [0 to 2.0 micrograms/g of air]), NO2 in air (0 to 5.5 ppm [0 to 8.8 micrograms/g of air]), or NO and NO2 in air. Bacteria grown under air only were used as controls. After incubation, the colonies that developed on the plates were counted. None of the bacteria tested was affected by NO or NO2 at the indicated concentrations while growing on nutrient agar. Serratia marcescens, B. circulans, B. subtilis, B. megaterium, and B. cereus grown on mineral salts glucose agar were not significantly affected by NO or NO2. Low concentrations (0 to 1.9 ppm) of NO were bacteriostatic to log-phase cultures of M. roseus, M. luteus, and Staphylococcus aureus grown on mineral salts glucose agar. Bacteriostatic activity over a 24-h interval was maximal at an initial NO concentration of 1 ppm. Appreciable amounts of NO2 were produced in 24 h at initial NO concentrations greater than 1 ppm. These results suggest that NO2 may reduce the bacteriostatic activity of NO. Low concentrations (0 to 5.5 ppm) of NO2 in air did not affect any of the bacteria tested. At these low concentrations, NO affected bacterial growth, although NO2, NO2-, and NO3- did not. In addition, it was determined that the bacteriostatic activity observed in this study was not due to an increase in the acidity of the medium.     

Results of the storage of freeze dried microbial cultures for 25 years

Saprophytic microorganisms belonging to different physiological groups (Azotobacter, acetic, ammonifying, lactic and nodule bacteria, a phototrophous purple bacterium of the Chromatium genus, bacteria of the Micrococcus and Pseudomonas genera, and a yeast of the Candida genus) were stored at 3-6 degrees C for 25 years in the freeze-dried state. All of the strains were found to be viable after the storage. The number of viable cells decreased for some bacteria, but to a far less degree than when the cultures were kept immediately after the freeze-drying for a year at 30 degrees C.     

Ultrastructure of two oil-degrading bacteria isolated from the tropical soil environment

Two oil-degrading bacteria identified as Pseudomonas aeruginosa and Micrococcus luteus were isolated from crude-oil-polluted soils in Nigeria. The organisms were grown on n-hexadecane and sodium succinate and then examined for the presence of hydrocarbon inclusions. Inclusion bodies were found in n-hexadecane-grown cells and were absent in succinate-grown cells. Formation of hydrocarbon inclusion bodies appears to be a general phenomenon among hydrocarbon utilizers.     

Ureolytic bacteria in sheep rumen.

Estimates were made of the numbers of viable bacteria in the rumens of sheep receiving different rations. Representative colonies were isolated and tested for urease production. Some urease-positive isolates were characterized and identified. The ureolytic activities of the urease-producing isolates were determined and compared with the activity of rumen fluid. The rations fed to the sheep did not exert a significant influence on the relative numbers of the urease-producting organisms in the rumen. No obligately anaerobic ureolytic bacteria were found. All urease-positive isolates were facultatively anaerobic, Gram-positive, catalase-positive cocci. Out of ten isolates, nine were identified as Staphylococcus saprophyticus and one as Micrococcus varians. The total urease activity of the different isolates based on the lowest numbers in which they were present in the rumen, compared favourably with the urease activity of rumen fluid. The facultatively anaerobic Gram-positive cocci were probably responsible for a large proportion of the urease activity of the rumen fluid. Conditions prevailing in the rumen were found to be conducive to urease production by the isolates tested.     

Heterotrophic bacterial populations in the mineral waters of thermal springs in Spain

The microbiological quality and heterotrophic bacterial populations of 26 thermal mineral water springs in Spain were studied. In most of the springs the number of viable aerobes was less than 10³ cfu ml^-1 and the number of sporulated bacteria less than 10² cfu ml^-1. No significant differences were foundin the counts obtained with Plate Count Agar (PCA) and PCA diluted 1 : 10 and incubated at 22°, 37° and 45°C. Total coliforms were found in 14 springs, faecal streptococci in three, spores of sulphite-reducing Clostridium and Pseudomonas aeruginosa in seven. Neither Escherichia coli nor Staphylococcus aureus were found. A total of 665 strains were isolated and 85·4% of these identified; 329 were Gram-positive and 239 were Gram-negative. The genera most prevalent present in the springs were Pseudomonas (in 92.3%), Bacillus (65.4%), Enterobacter, Micrococcus and Staphylococcus (50%), Acinetobacter (42.3%), Arthrobacter (38.4%), Clostridium (27%) and Xanthomonas (23%). Gram-negative bacteria predominated in the mesothermal springs and Gram-positive bacteria in the hyper- and hypothermal springs. The most common Gram-negative rod species isolated were Ps. fluorescens, Ps. aeruginosa, Ps. putida, Ent. agglomerans, Ent. sakazakii, Ac. calcoaceticus and Ent. amnigenus.     

Differential involvement of mussel hemocyte sub-populations in the clearance of bacteria

Mussels are filter-feeders living in a bacteria-rich environment. We have previously found that numerous bacterial species are naturally present within the cell-free hemolymph, including several of the Vibrio genus, whereas the intra-cellular content of hemocytes was sterile. When bacteria were injected into the circulation of the mussel, the number of living intra-hemocyte bacteria dramatically increased in less than an hour, suggesting intense phagocytosis, then gradually decreased, with no viable bacteria remaining 12h post-injection for Micrococcus lysodeikticus, 24h for Vibrio splendidus and more than 48 h for Vibrio anguillarum. The total hemocyte count (THC) was dramatically lowered by the bacterial injections, as quantified by flow cytometry. V. splendidus induced the strongest decreases with -66% 9h post-injection of living bacteria and -56% 3h post-injection of heat-killed bacteria. Flow cytometry was used to identify three main sub-populations of hemocytes, namely hyalinocytes, small granulocytes and large granulocytes. When THC was minimal, i.e. within the first 9h post-injection, proportions of the three cell categories varied dramatically, suggesting differential involvement according to the targets, but small granulocytes remained the majority. According to a decrease in their number followed by an increase (+90% at 12h with living V. splendidus), hyalinocytes also appeared to be involved as cellular effectors of antibacterial immunity, despite possessing little capacity for phagocytosis and not containing antimicrobial peptides.     

Faculative Anaerobic Bacteria in the Digestive Tract of Chum Salmon (Oncorhynchus keta) Maintained in Fresh Water Under Defined Culture Conditions

The bacterial flora in the digestive tract of chum salmon growing in fresh water under defined and controlled culture conditions was examined both qualitatively and quantitatively. The predominant species present in the digestive tract were identified as Aeromonas, with Aeromonas hydrophila being the most common isolate. These aeromonads were not isolated from the diet. Other bacterial species commonly isolated included Bacillus, Enterobacter, nonpigmented pseudomonads, Micrococcus, and Acinetobacter. These species were also isolated from the diet or tank water. As many as 10-8 viable bacteria per g (wet weight) of digestive tract plus contents were counted. After 75 days of starvation, 10-6 viable bacteria were counted, whereas fish fed a sterile feed contained 10-5 viable bacteria per g (wet weight) of digestive tract plus contents.     

Exploring the potential environmental functions of viable but non-culturable bacteria

A conventional plate count is the most commonly employed method to estimate the number of living bacteria in environmental samples. In fact, judging the level of viable culture by plate count is limited, because it is often several orders of magnitude less than the number of living bacteria actually present. Most of the bacteria are in “viable but non-culturable” (VBNC) state, whose cells are intact and alive and can resuscitate when surrounding conditions are more favorable. The most exciting recent development in resuscitating VBNC bacteria is a bacterial cytokine, namely, the resuscitation-promoting factor (Rpf), secreted by Micrococcus luteus, which promotes the resuscitation and growth of high G+C Gram-positive organisms, including some species of the genus Mycobacterium. However, most of studies deal with VBNC bacteria only from the point of view of medicine and epidemiology. It is therefore of great significance to research whether these VBNC state bacteria also possess some useful environmental capabilities, such as degradation, flocculation, etc. Further studies are needed to elucidate the possible environmental role of the VBNC bacteria, rather than only considering their role as potential pathogens from the point view of epidemiology and public health. We have studied the resuscitation of these VBNC bacteria in polluted environments by adding culture supernatant containing Rpf from M. luteus, and it was found that, as a huge microbial resource, VBNC bacteria could provide important answers to dealing with existing problems of environmental pollution. This mini-review will provide new insight for considering the potentially environmental functions of VBNC bacteria.     

Stereoselective epoxidation of phenyl allyl ether by alkene-utilizing bacteria

Summary Eighteen newly isolated ethene- and propene-utilizing bacteria were screened for the ability to produce phenyl glycidyl ether, a common precursor for the synthesis of beta blockers, from phenyl allyl ether. These organisms included Aerococcus, Alcaligenes, Micrococcus and Staphylococcus spp. and a variety of Gram-negative, Gram-positive and Gram-variable mesophilic rods/coccobacilli not yet identified. The majority of ethene- and propene-grown cultures (14 strains) accumulated phenyl glycidyl ether (0.4–1.7 mm) as the sole oxidation product. The bioconversions with the three most promising ethene-utilizers (M26, M90C, M93A) were scaled-up to yield essentially optically pure (enantiomeric excess = 93%) S-(+)-phenyl glycidyl ether. This is currently under investigation for commercial production of optically pure beta blockers. Offprint requests to: M. Mahmoudian     

The role of encapsulated anaerobic bacteria in synergistic infections

Abstract: The effect of encapsulation on the virulence, survival, and protection of anaerobic bacteria from phagocytosis is reviewed. Support for the importance of encapsulated Gram-negative anaerobic rods ( Bacteroides sp., Prevotella sp. and Porphyromonas sp.), anaerobic and facultative Gram-positive cocci (AFGPC) was provided by their higher recovery rate in oropharyngeal infections, abscesses and blood, compared to their number in the normal flora. The pathogenicity of Bacteroides, Fusobacterium, Clostridium , and AFGPC was studied by inoculating them into mice and observing their ability to induce subcutaneous abscesses. Encapsulated Bacteroides, Fusobacteria , and AFGPC generally induced abscesses, whereas non-encapsulated organisms did not. However, many of the strains that had only a minimal number of encapsulated organisms (< 1%) survived in the abscesses, and they became heavily encapsulated when inoculated with other viable or non-viable encapsulated bacteria. Thereafter, these strains were able to induce abscesses when injected alone. Encapsulated Gram-negative anaerobic rods and AFGPC-induced bacteraemia and translocation, and increased the mortality of the infected animals more often than did the non-encapsulated form of the same strains. As determined by using selective antimicrobial therapy and quantitative cultures of abscesses induced in mice, possession of a capsule generally made Gram-negative anaerobic rods more important than their aerobic counterparts. Synergistic potentials were seen between encapsulated Gram-negative anaerobic rods and all tested aerobic bacteria and most AFGPC, and also between most AFGPC and Pseudomonas aeruginosa or Staphylococcus aureus . These studies demonstrated the importance of encapsulated anaerobes in mixed infections.     

A Note on the Microflora of Beef Muscle Stored in Nitrogen at 0°

Fresh beef stored in nitrogen at 0° was spoiled by Gram positive rods. Almost all the organisms isolated were Microbacterium spp., although in one experiment about 10% of the organisms isolated were Lactobacillus spp. The numbers and types of organisms isolated were similar on each of two media incubated under aerobic and anaerobic conditions.     

Microbiology of Drycleaning

An appreciable number of bacteria on contaminated fabric survived modern drycleaning procedures. Various stages in the process, especially steam pressing, reduced the total number of bacteria, but viable organisms were found on certain areas of garments even after pressing. A significant number of bacteria were redeposited on clean fabric during the washing of ordinary soiled garments in drycleaning units. These bacteria included gram-positive cocci, diphtheroid bacilli, and gram-positive sporeformers. Gram-negative bacilli were seldom found, although some gram-negative bacilli survived drycleaning. The redeposited organisms apparently came mainly from other garments in the same loads, as few bacteria were isolated from the filtered solvent used for washing. The number of bacteria in the drycleaning washwheel was highest shortly after the beginning of the wash, and decreased, with the exchange of solvent in the wheel, to a low level at the end. Although it appears that in most cases several factors combine to reduce to a low level the numbers of bacteria on articles cleaned in a well-operated drycleaning plant, it would seem that under certain conditions pathogenic microorganisms could be disseminated by drycleaning.     

Microbiology of Drycleaning

An appreciable number of bacteria on contaminated fabric survived modern drycleaning procedures. Various stages in the process, especially steam pressing, reduced the total number of bacteria, but viable organisms were found on certain areas of garments even after pressing. A significant number of bacteria were redeposited on clean fabric during the washing of ordinary soiled garments in drycleaning units. These bacteria included gram-positive cocci, diphtheroid bacilli, and gram-positive sporeformers. Gram-negative bacilli were seldom found, although some gram-negative bacilli survived drycleaning. The redeposited organisms apparently came mainly from other garments in the same loads, as few bacteria were isolated from the filtered solvent used for washing. The number of bacteria in the drycleaning washwheel was highest shortly after the beginning of the wash, and decreased, with the exchange of solvent in the wheel, to a low level at the end. Although it appears that in most cases several factors combine to reduce to a low level the numbers of bacteria on articles cleaned in a well-operated drycleaning plant, it would seem that under certain conditions pathogenic microorganisms could be disseminated by drycleaning.