Colony (microbiology)

“ Our ponds can furnish no more extraordinary object for our microscope than a colony of Cristatella Mucedo; it is curious in appearance and still more curious from the fact that though a colony of animals it acts like a single individual in crawling over the weeds and stones in shallow, sun-kissed water. The Cristatella colony is jelly-like and greenish in colour, in length it may grow to a couple of inches. Its under surface is flat, whilst from its upper, convex surface the little animals forming the colony wave their brush-like tentacles in the water. ”

“ The colony when very young appears as a pale and small spot, not completely spherical as other bacterial colonies in gelatine are wont to be, but with a more or less irregular, protruding, or jagged contour. ”

“ Suppose we take milk, water, butter, anything in fact upon which bacteria will grow and examine them carefully. If we have the requisite knowledge and recognise what we see, we shall find not one kind of bacterium but a number of different bacteria. Now by certain manipulations, which need not be described here, all the different kinds of bacteria may be sorted out, so that we have colonies consisting of one kind of bacterium only and such a colony is known as a “pure culture.” ”

“ The colony (Fig. 10, A) is a hollow sphere, the numerous green cells of which it is composed forming a single layer on the outside. By killing with iodine, and using a strong lens, each cell is seen to be somewhat pear-shaped (Fig. B) , with the pointed end out. Attached to this end are two vibratile filaments (cilia or flagella) , and the united movements of these cause the rolling motion of the whole colony. Usually a number of young colonies (Fig. x) are found within the mother colony. ”

“ To prevent the disease from spreading in a colony there is no more reliable and efficient process than to stop the production of brood; for where no brood exists none can perish or putrefy. The disease is thus deprived both of its aliment and its subjects. ”

“ In the mud of our pond we may find a little colony of plants which might forgivably be mistaken for a collection of the individuals we have just studied. Each member of the colony is very much smaller than Chlamydomonas to be sure, but each one has the outer membrane, the brownish eye spot and the pair of little whips. On the other hand the chlorophyll fills the whole of each cell and is not arranged in the form of a cup. Sixteen cells form a colony, and the whole mass is a flat plate; the little whips move in unison and the whole colony revolves after the manner of a wheel. ”

“ To study further the peculiarities of the different bacteria, small portions of the individual colonies are transferred to tubes of sterile culture-media. In order to do this the colony is touched with a piece of platinum wire; the minute amount of growth that adheres to the wire is sufficient to seed the tube of fresh culture-medium. The inoculating needle must always be sterilized before use by passing it through a gas flame. ”

“ These have each an eye-spot, a contractile vacuole, and two flagella, by the combined action of which the colony is propelled. Delicate boundary lines in the colonial wall mark out the proper investment of each cell. The cells give off delicate plasmic threads which meet those of their neighbours, and form a bond between them. ”

“ In this method the bacteria are distributed in a gelatine or agar medium liquefied by heat, and the medium is then poured out on sterile glass plates or in shallow glass dishes, and allowed to solidify. Each bacterium capable of growth gives rise to a colony visible to the naked eye, and if the colonies are sufficiently apart, an inoculation can be made from any one to a tube of culture-medium and a pure culture obtained. ”

“ As soon as it becomes thoroughly established on a host plant, the many little branches, waving about like the shoot produced from the seed, attach themselves to other plants, and thus the colony is increased in size. In legumes, the host plant first attacked soon dies, but before this occurs, the parasite has become firmly established on adjoining plants and is reaching out and completing the colony. ”

“ But it is not with these beneficent or great industrial classes of bacteria that we are now more immediately concerned, but rather with the malevolent varieties, or the so-called "submerged tenth," for which no labour colony has at present been created to direct their energies into useful and profitable channels. ”

“ It consists of a large number of conical or pear-shaped individual cells, whose apices are turned toward the centre of the sphere. The cells are cemented together by a mucilaginous substance. Around their exposed larger ends, which form the surface of the sphere, are rows of flagella, by whose united action the colony rolls through the water. After a time each individual absorbs its flagella, the colony is broken up, the different individuals settle to the bottom, and each gives rise by division to a new colony. This group of cells may be considered as a colony or as an individual. ”

“ Restrictions, to prevent the introduction of infected vines, were wise when the vines in the colony were free from any infection; but, now that the disease exists, what is the good of those prohibitions? ”

“ Reproduction.—The formation of colonies by gemmation has frequently been mentioned above. The young buds of a colony arise from the endoderm canals in the body-wall of the zooids, in the general coenenchym, or in the stolon. They never arise from evagination of the coelenteric cavities of the zooids. There is no evidence that fission of a colony to form secondary colonies ever occurs. Gemmation leads to the increase in the number of zooids forming a colony, but not to an increase in the number of colonies. ”

“ The disease rapidly spreads to surrounding cells and combs, if allowed to take its course, till finally no brood can hatch, and the colony succumbs. On opening some of the cells a thin glue-like coffee-coloured mass will be noticed, which on the insertion of a splinter of wood will adhere to the point, and can be drawn rope-like for some little distance out of the cells. ”

“ This leveling is an important matter since the development of a colony is to some extent proportionate to the supply of medium available for its nutrition. Thus in a "smear" on sloped tube culture, the colonies at the upper part of the medium are stunted and small but increase in size and luxuriance of growth the nearer they approach to the bottom of the tube, where there is the greatest depth of medium.
Fig. 122.—Plate-levelling stand. ”

“ As to to the quantitative examination, that is fulfilled by counting the number of colonies which appear, say by the third and fourth day, upon the gelatine plates. Each colony has arisen, it is assumed, from one individual, so that if we count the colonies, though we do not thereby know how many organisms we have upon our plate, we do know approximately how many organisms there were when the plate was first poured out, which are the figures we require, and which can at once be multiplied and returned as so many organisms per cubic centimetre. ”

“ Supposing that the hypothetical colonies, which were at first entirely made up of similar cells, were to gain some advantages, if in the course of development, the molecules of the reproductive cells, from which each colony arose became distributed irregularly in the resulting organism, there would be a tendency towards the perpetuation of such a change, wherever it appeared as the result of individual variability. ”

“ Others are in colonies that spread by extensions of the base from which arise other hydroids until a bunch of them are growing side by side; but these groups consist of hydroids differentiated into separate [Pg 35] functions, for some devote themselves to capturing food which nourishes all, through the common base, while others produce the buds and eggs by which the colony is increased. ”

“ For when the air is lighter, or the same as the particles of disease or odor, it simply moves or floats around, and woe be to the hive or colony that chances to be in its way!
Now here, in regard to that disease, I will give some food for thought. Why do not such colonies of bees, that rob foul-broody colonies, always become affected with the disease? I imagine I hear a long list of persons who answers “They do;” ”

“ Among the cells of the young colony some cease to divide, but continue to grow at an early period, and these are destined to become in turn the mothers ("parthenogonidia") of a new colony; they begin segmenting before the colony of which they are cells is freed. The young colonies are ultimately liberated by the rupture of the sphere as small-sized spheres, which henceforth only grow by enlargement of the sphere as a whole, and the wider separation of the vegetative cells. Thus the vegetative cells soon cease to grow ”

“ They reach out and involve all kinds of tissue which happen to be near them; they infect the blood, and new colonies form at points situated at a distance from the parent growth. There is hardly a doubt but that malignant growths are quite local at the outset, but, like red ants, the microbes make more and more nests in the same field. As with red ants, too, we often fail to eradicate the colony, because many members may be away from home at the time when the nests are destroyed. ”

“ On all occasions, under this practice, a proper temperature may be supported in a colony; and in all critical points, by a just observation of the state of the thermometer, Bees may be relieved and assisted, and all the mischiefs attending the old mode of management may be guarded against and prevented. For when adequately relieved and properly assisted, they proceed to rid the colony of all embryo Queens, which would only become so many supernumeraries in a hive where the reigning Queen is fertile, and the necessity for emigration is superseded. ”

“ It has a rosy color, and, being very small, it looks, until one examines it closely, more like a thick red carpet of soft moss, than like a colony of animals. These communities are distinct in sex, the fertile individuals in each being either all male or all female. In Fig. 100 we have a portion of a female colony, representing one fertile head, in which the buds are crowded with Medusæ; one sterile head, surrounded by its wreath of tentacles; and still another member of the society whose office is not fully understood, unless it be that of a kind of purveyor, catching food for the rest. ”

“ The facts at our disposal indicate that the germ-cells only appear, for the first time, after embryological development, in those cases where the formation of asexually produced colonies takes place, either with or without alternation of generations; or in cases where alternation of generations occurs without the formation of such colonies. In a colony of polypes, the germ-cells are produced by the later generations, and not by the founder of the colony which was developed from an egg. ”

“ Their life processes and ecological interactions can't be easily observed directly in the soil with a microscope. Usually, scientists study microorganisms by finding an artificial medium on which they grow well and observe the activities of a large colony or pure culture—a very restricted view. There probably are more species of microorganisms than all other living things combined, yet we often can't identify one species from another similar one by their appearance. We can generally classify bacteria by shape: round ones, rod-shaped ones, spiral ones, etc. ”

“ This process may be repeated a number of times until a colony of shelled amœbæ, of varying pattern in [24] different species, may be formed and permanently associated together (Fig. 4) . The individual amœbæ are all alike and perform the same functions. There is no division of labor, no specialization, among them. If the individual animals could be separated from one another they would live and build new colonies.
Pandorina morum forms a small colony of sixteen cells (solid sphere) of mulberry-like shape and enclosed in a common gelatinous envelope. ”

“ In the next higher class of colonial protozoa, the first differentiation of the members or cells of the colony takes place. One part of the cells is set apart to continue the task of reproduction, while the main body of the colony does not participate any longer in the function of generation. As a rule, the reproductive cells are divided into two kinds, and these two kinds of cells conjugate with each other. The conjugation takes place either between different members of the same colony or between members of different colonies of the same species. ”

“ It is very probable that numerous symbiotic fermentations in the soil are due to this co-operation of oxygen-protecting species with anaerobic ones, e.g. Tetanus.
Fig. 21.—A plate-culture colony of a species of Bacillus—Proteus (Hauser) —on the fifth day. The flame-like processes and outliers are composed of writhing filaments, and the contours are continually changing while the colony moves as a whole. Slightly magnified. (H. M. W.)
Astonishment has been frequently expressed at the powerful Activity of bacteria. ”

“ Examine a colony of Vorticella in a watch-glass of water or in a drop of water on a glass slide under the microscope. Note the stemmed bell-shaped bodies which compose the colony. Each bell and stem together form an individual Vorticella (fig. 8.) How are the members of the colony fastened together? Tap the slide and note the sudden contraction of the animals; also the details of contraction in the case of an individual. Watch the colony expand ”

“ Its effect is to produce large colonies, such as the great beds of Reeds (Phragmites) or Reed-mace (Typha) which fringe our lakes, the groves of Bent (Ammophila) on sand dunes, and the beds of Anemones (A. nemorosa) or Broad-leaved Garlic (Allium ursinum) of our spring woods. In all these cases the whole colony may be the result of the continued growth of a single individual. It should be noted, however, that such migration is possible only so far as favourable soil conditions extend. ”