BACTERIA FOUND IN THE AIR OVER THE ATLANTIC OCEAN1

Abstract Two return flights were made across the Atlantic Ocean from Montreal to

London, England, and aerobiological samples mere talcen a t intervals throughout the flights. This publication deals with the bacteria isolated during these flights. The bacteria were found to be very much like those found over land and included the following genera: Psezcdontonas, Flavobacterium, Achromobacter, Cory~tebacterium, Micrococczcs, Sarci7ta, and Bacillus.

Since 1947 four aerobiological studies have been carried out on the inicro- organisms in arctic and non-arctic parts of Canada as well as in Alaslia and over the Arctic Ocean. The types of fungi (5) and bacteria (2) found nrere apparently of soil origin and many forms remained suspended in the air for a considerable time. The results of exan~iilatio~l of various types of air a t different periods of the year indicate that in time the microorgallisms died in a certain order and the air eventually became sterile. Air that had beell over the arctic for a considerable time, as \\.ell as winter air, carried small nunlbers of the more resistant types of microorganisms. The fungi in such air were few in numbers or not present, indicating that they had a lower resista~lce than the bacteria. The sporeformers showed the greatest resist- ance a i d a t times u-ere the only organisins present. Because of possible recontamination of the air from soil, it was difficult a t times to determine with certainty ~vllich organisms had survived and which had been inore recently swept into the air. Though Zobel has shown (8) that bacteria from the ocean may be found in maritime air, sainpling from the air over the ocean seemed to present the best possibility of determining survival types. Antarctica, since it is far removed from arable land by wide stretches of water, would seem to be an ideal place for such sampling. However, Darling and Siple (1) fouild the air, a t ground level, to be practically sterile, with sporeforrni~lg bacteria and Aclzromobacter species the few remaining organisms.

I t seemed desirable to collect samples over the ocean, and therefore two sampling flights, over the Atlantic Ocean between Montreal and London, England, were carried out in June and August 1951 (6). The June flight was by way of Goose Bay to London and from London to Iceland, to Green- wood in Nova Scotia, and back to hlontreal. The August flight was by way of Goose Bay to London and the return to R'lontreal, by way of Iceland and Goose Bay. Flights \Irere a t eight and nine thousand feet. All air masses \Irere recorded and later correlated with the samples.

The technical data of the flight itself was recorded earlier (6) and will not be repeated in detail here. Samples were taken by the McGill G.E. sampler (2) oilto Petri dishes containing modified Czapeli's agar and ~vi th air filters

'Manuscript received December 26, 1956. Contribution from the Department of Bacteriology, McGill University, Montreal, Quebec.

The writers gratefully acknoivledge the support of the Defence Research Board in providing a grant (No. 175) for this work.

Can. J. Microbiol. 3 (1957)

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458 C.J.N.-\DI:\N JOURNAL O F MICROBIOLOGY. VOL. 3. 1957

TABLE I

Gram- Gram- negative positive

rods rods Micrococci Sporeformers Air - -

Flight masses No. % No. % No. Oib No. %

June Tropical 8 6 . 5 24 19.5 36 29.2 55 44.7 Polar 2 1 . 8 13 11.6 78 69.2 19 17.0

August Tropical 17 18.1 44 46.9 13 13.8 20 21.2 Polar 17 19.7 20 23.3 11 12.8 38 44.2

which were later plated on Czapek's agar. The samples were incubated for 5 days a t room temperature. All colonies mere isolated and studied. The cultures were divided into groups of Gram-negative rods, Gram-positive pleomorphic rods, staphylococci, and sporeforming rods, and the percentage of each group of organisms are reported in Table I. The bactcria were also classified into genera and species and recorded in the results.

Results

The numbers of bacteria in the Atlantic air were very low and counts per cubic foot varied froin 0 . 0 to 0 . 5 in polar air masses and 0 .3 to 0 . 9 in tropic air, so it was difficult to esti~nate percentages of bacterial species from such low numbers. The fungus counts were somewhat higher, being 0.05 to 2 . 6 per cu. ft. in polar air and 0 . 2 to 9 .0 in ti-opical air. Somewhat similar counts were found in air over non-arctic Canada in summer time (3).

Pacly and Icapica reporting on the fungi over the Atlantic (4) considered that the number of non-viable fungus spores on silicon slides, as compared with the number of viable spores on agar plates, gave a goocl indication of the history of an air inass or the length of time since the air had piclied up spores by passing over cultivated land. As there was no method available for estimating non-living bacteria in the air, it was not possible to inalce such a comparison with the bacteria. However, the percentage of certain types of bacteria docs give some indication of the histor)- of air masses. The percentages of the different t)-pes for polar and tropical air are given in Table I . There were vei-1. few Sarcina found on the plates excepting or1 one plate which contained 49 Sauc,inn froin tropical air and no other organisms. This plate was eliminated from the averages, but some of the orga~lisms have been identifiecl.

The species of bacteria were the same as found in air inasses over land but were i~lclinecl to be fewer in numbers. The numbers in tropical air were higher than in polar air and there was a cliffereilce in the ratio of types (Table I).

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KELLY AND LAX'NE: BACTERIA I N AIR 459

June Flights Two hundred and four organisms were isolated and identified as completely

as possible: five were species of Pseudomonas but could not be identified further; two were species of Flavobacterium ( F . breve and F. arborescens); three cultures of Achrornobacter liqz~efaciens were found. One Gram-negative rod was lost before it could be identified.

Thirt~i-eight species of Gram-positive pleomorphic rods were all placed in the genus Corynebacterium. Eleven were C. simplex, nine were C. helvolum, and six were C. tumescens. Twelve could not be identified as to species but could be talten only as far as the genus.

One hundred and four cultures were placed in the genus il!ficrococcus, and 13 species of Sarcina were isolated and the species determined where possible. Ten were classified as AC. saccatus, seven as iM. freudenreichii, 13 as M. ureae, one as 111. nitrificans, four as M. flavus, 13 as M. candidus, nine as M. varians, seven as M. Iziteus, six as M. epidermidus, two as M. az~ranticz~s, one as ill. albus, and four could not be carried farther than the genus. The Sarcina were three S. lutea, one S . az~rantiaca, one S. lactea, two S . sz~bfiava, one S. conjunctivae, and four were unclassified as to species. The genus Bacil lz~s was represented by 42 species. The species were 15 B . brevis, 30 B . cereus, 10 B . megateriz~m, two B . macerans, six B . subtilis, one B . polymyxa, and eight species which could not be identified.

. lugust Flights On these flights 180 orga~iis~ns were isolated and classified. The Gram-

negative rods were represented by a total of 35 strains of which Alchronzobacter eurydice was represented by five strains and Flavobacteriz~m n a a r i n ~ ~ m by one strain. Twenty-seven were strains of Pseudomonas that could not be classified beyond the genus and tivo could only be classified as Gram-negative rods.

The Gram-positive pleomorphic rods were represented by 65 species and were broken down as 20 species of Corynebacteriz~m simplex, 17 as C. heluolum, one C. f imi, two C. tumescens, one C. filamentosum, and 24 unclassified Corynebacteria.

The 24 micrococci \Irere classified as four M. caseolyticz~s, two as h1. candidus, seven as M. epidermidz~s, one M. luteus, one M. j'lavz~s, two M. ureae, one B1. saccatus, one 114, az~rantiacus, three M. varians, one M . albus, and one unclassified.

Discussion and Conclusions

At eight thousand to nine thousand feet the number of bacteria found over the ocean was much the same as found over land, over the ocean there was less chance, however, that there had been fresh inoculation. The bacteria isolated on both flightsnrere common soil types that could be found by sampling soil a t random.

After these bacteria from over the AtlanticOcean were isolated and classified, it was concluded that they were very similar to those found over land. I t was also felt that groups of similar organisms would give as much information

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460 CANADIAN JOURNAL O F MICROBIOLOGY. VOL. 3, 1957

as would the species completely classified. Therefore, in Table I the bacteria are reported as Gram-negative rods, Gram-positive pleomorphic rods, Gram- positive pleomorphic rods, micrococci, and sporeformers.

The ratio of the types of bacteria could be used to some extent to trace the history of an air mass. The tropical air tended to show a higher percentage of Gram-negative rods and Gram-positive pleomorphic rods than micrococci and sporeformers, while arctic air tended to show the opposite.

References 1. DARLING, C. A. and SIPLE, P. A. Bacteria of Antarctica. J. Bacterial. 42, 83-98 (1941). 2. KELLY, C. D. and LAYNE, S. Bacteria in Canada and the American Arctic. Can. J

Microbial. 3. (1957). 3. KELLY, C. DI and PADY, S. M. Microbioiogical studies of air over some non-arctic regions

of Canada. Can. J. Botany, 31, 90-106 (1953). 4. PADY, S. M. and I ~ P I C A , L. Fungi in air over the Atlantic Ocean. hlycologia, 47, 34-50

tin<<\ \*."",. 5. PADY, S. Wf. and KAPICA, L. Air-borne fungi in the Arctic and other parts of Canada.

Can. 1. Botanv. 31. 309-323 (1956). 6 . PADY. S. $4. and K E L ~ Y . C. D. ' ~erdbiological studies of fungi and bacteria over the

-.- \ -,--,. 8. ZOBELL, C. E. and MATHB~VS, H. M. A quantitative s t ~ ~ d y of the bacterial flora of sea

and land breezes. Proc. Natl. Acad. Sci. U.S. 22, 567-572 (1936).

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