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genus belong species which form white, yellow, red or brown colonies.

Sarcina maxima, Lindner, is found in malt mashes. The cells are 3 to 4 μ in diameter.

Sarcina aurantiaca, Lindner, has been isolated from Berlin "Weissbier". This species, as also S. flava and S. alba, is said to give rise to diseases in American beer.

The species belonging to the two foregoing genera are very common in nature, and occur, among others, also in water. Jorgensen and Lindner, for example, found these forms in their water analyses. Their occurrence in breweries has been mentioned above.

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II.-FAMILY: ROD BACTERIA (BACTERIACEÆ).

The cells are of various lengths, cylindrical and straight never spiral. Fission takes place only in one direction, viz., transversely, and after previous elongation of the rod.

Genus 1 and 2: Bacterium and Bacillus.

The older systematists, Cohn for example, called all short rods Bacteria, all long rods Bacilli. At present it is impossible to separate the two genera completely from one another by this means. For the species appear sometimes as short, sometimes as long rods. The author, however, retains both these generic names on practical grounds, the species being hence represented with their old names; so that, for example, the generic names Granulobacter, Clostridium, etc., are retained in what follows. For distinguishing purposes the spore formation and the flagella have been

suggested; but these characteristics also have proved to be insufficient.

Acetic Acid Bacteria.

Kützing (1837) first described an acetic acid bacterium, whilst Hansen was the first to show that various species of acetic bacteria exist, and to give at the same time. the outlines of their life history (1879). The investigations of A. J. Brown, Henneberg, Zeidler and Zopf show that a few of these species have a swarming state under certain conditions. One of these acetic acid bacteria with flagella is shown in Fig. 135. In this case the flagella are of particular importance in characterising the species. With some species the mucilage which is formed by the cells gives a blue reaction with iodine (Hansen), that of others yields the cellulose reaction (a blue stain with iodine and sulphuric acid; A. J. Brown).

Hansen has given information on the vitality of these bacteria in different nutrient media and also in the dry state. He found that Bacterium aceti lived in "double' beer more than six years, in some cases, however, not five years; further, that after nine years in lager beer and after about two years in a saccharose solution it was still alive; Bacterium Pasteurianum was alive after six years (in one case it was dead after two and a quarter years) in "double" beer, after more than ten years (in one case death occurred after one to two years) in lager beer, and after one year and a quarter in a saccharose solution; but in the latter it was dead after one year and a half; lastly, Bacterium Kützingianum was alive after about six years in "double "beer (in some cases it was dead after five years), and after about seven years in lager beer (in some cases after five years only). In the dry state on small pieces of platinum wire in Freudenreich flasks the life limit of the cells of the three

species named was about five months. When the abovementioned dry preparations were introduced into glass tubes, and these closed by fusing, and preserved at the ordinary room temperature and at 2° C., it appeared that the lifetime at the former named temperature was about five months, and more than a year at the latter. When the cells were introduced into the tubes in a moist state they very soon died.

The formation of acetic acid induced by these organisms is brought about by the alcohol being converted into acetic acid in the presence of a plentiful air supply. As Pasteur showed (1864), and A. J. Brown confirmed later, the combustion can proceed still further, so that the acetic acid already formed is oxidised to carbonic acid and water.

F. Lafar studied the influence of temperature on Bact. aceti and Bact. Pasteurianum with regard to their power of forming acetic acid. He found that the former species at as low a temperature as 4° to 5° C., the limit of its growth, can set up a strong acetic fermentation, but that Bact. Pasteurianum, on the other hand, formed no acetic acid at 4° to 44 C. With the last-named species he found, further, that the maximum acid formation is reached at 33° to 34° C. after seven days, when 3.3 per cent. by weight is produced. W. Seifert came likewise to the conclusion that morphologically different species of acetic acid bacteria also exhibit substantial differences in regard to their chemical behaviour. In his experiments he employed Bact. Pasteurianum and Bact. Kützingianum. He draws the conclusion, "that the fermentative power of acetic acid bacteria in the presence of the monatomic primary alcohols decreases as the proportion of carbon in the latter increases; that, further, Bact. Pasteurianum has the feeblest fermentative power in the presence of the polyatomic alcohols and dextrose". Henneberg carried out investigations similar to Seifert's, but with

a whole series of species of which some are new: he arrived at the same general result,

In the following table from Henneberg will be found numerous substances which can be converted into acids by the various species. The sign+indicates that acidification, that no acidification takes place.

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The variation in shape with the same species, according

as the temperature lies near the optimum or the maximum, has been referred to previously (p. 319; cf. Figs. 138, 139 and 140), and also the variation of the iodine reaction of the mucilage.

We have also seen that acetic acid bacteria cause the sharpness of wine and that they only give rise to loss in breweries when a high temperature and free air access are obtainable.

Pasteur (1868) was of the opinion that acetic fermentation was caused by only one species. He worked out a new method for the manufacture of vinegar, to displace the old Orleans method in which the fermentation

proceeded slowly in barrels. As these barrels were employed for several years without emptying and cleansing, large quantities of Vibrio aceti were frequently developed, which caused considerable trouble. The Pasteur method consisted in using shallow vessels instead of barrels; he thus endeavoured to provide the most favourable conditions for the development of the film of acetic bacteria and by this means to bring about as quickly as possible the formation of vinegar so that the Vibrio aceti could not develop. For various reasons the method did not, however, obtain a foothold in practice, partly because the results obtained were so uncertain since here was no question of the application of a selected species or race. In the first edition of his Untersuchungen aus der Praxis der Gärungsindustrie, Hansen had, in this connection, already directed attention to the problem of also applying the pure culture system to the manufacture of vinegar; but only of late has the way been paved for reform in this direction by the researches of the experimental station in Berlin; the goal has not yet been reached, however. The question here concerns the most important method

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FIG. 143.-Bacterium aceti (Kütz.), Hansen. Young film formation on "double beer at 34° C. 1999. (After Hansen.)

of vinegar manufacture, i.e., the so-called quick vinegar manufacture of Schützenbach. The acetic bacteria occurring in this connection will be described later.

Acetic bacteria naturally fall into groups according as they possess flagella or not, and according as their mucilage gives a blue reaction with iodine or not. In the following it is expressly stated if the species in question has flagella or gives the blue iodine reaction. The first three following, the descriptions of which are from Hansen, belong to species without flagella.

Bacterium Aceti (Kütz.), Hansen (Figs. 141, 143).-This species forms a smooth gelatinous film on "double" beer at

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