BACTERIA AND THEIR GROWTH

Shannon News, 20 December 1927, Page 3

BACTERIA AND THEIR GROWTH

FIFTEEN MILLIONS IN TWENTYFOUR HOURS. In the course of a lecture to the Palmerston Lunch Club, Mr L. F. Cooper, bacteriologist'at the Palmerston Hospital, put. into popular form some scientific facts relating to bacteria. “it is first necessary to realise that bacteria cannot, be seen with the naked eve,” said Mr Cooper in his opening remarks. “They are exceedingly minute and unicellular—that is, each individual germ' consisting of one cell is complete in itself for living purposes. It can eat, grow and multiply. Excluding accident, they are immortal. They reproduce themselves by . a process of s'mple division, an individual dividing and fwo daughter forms taking the place of the original parent one; and, although the parent has disappeared, here lias been no death. Its protoplasm or living material is still existent in *ts progeny and is immortal, since this process of reproduction may go on indefinitely.

THREE MAIN GROUPS

“Bacteria may firstly be considered in three main groups classified according to shape:—(l) Small round ones known as cocci; (2) rod or stick shaped as bae Hi; (3) spiral or corkscrew as spirilla. The unit of measurement applied to bacteria is the micron or micromillimeter. One of these equals onethousandth "part of a millimeter and one millimeter is equal to 25 parts' of an inch. Therefore, one micro-milli-meter is equal to 1.25,000 th part of an inch.

The cocci, the small round ones, range ill size in different species from a-half micro-millimeters to two micromillimeters in diameter. But most measure about one micro-millimeter or 25,000th part of an inch. The bacilli, the rod shaped ones, are usually not more than a 25,000 part.of an inch across, but vary greatly in their length. Some have square ends, and some rounded ends. Their inode of development oj’ the manner in which they increase their numbers is by a process of simple transverse fission. One single germ becomes elongated and divides in the centre, the result being two. They in turn undergo division, the Result being four and so on. This explains the external appearances of the division, but the internal changes are much different. Some phases or change in the internal structure and its ultimate distribution did and perhaps still provides a theory for the origin of sex. The rate of division varies slightly with the different, bacteria, but division takes place approximately every 20 minutes. For example, commencing with one germ, and if,division only takes place, every hour, it is estimated that, at the end of 24 hours, there will be 15 millions. During this process of division or multiplication, another factor presents itself _tlie growth being controlled or restricted to a certain shape according to the species. MOVEMENT OF BACTERIA.

“Motility, or the power of self propulsion,'is not common to all bacteria but. is chiefly confined to. the bacilli and spirilla. Movement is obtained by the moving of hair or whip-like organs known as flagella. These may be distributed all around the organism or only at one or both of the poles. It is estimated that the thickness of these flagella'measures' 1-204,000 th part of an inch. The non-motile organisms arc dependent on the movement of the fluid in which they may be suspended—moisture, etc. “A number of■»bacteria possess the power of developing into a kind of resting stage or spore formation. Only one spore develops in each cell, and the spores serve to perpetuate the race when it is threatened with extinction from adverse circumstances, such as unfavourable environment, or lack of nutrition. Each spore consists of a little mass of the body of the germ enclosed within a vferv tough and resisting wall or membrane which tends to preserve its vitality even under unfavourable conditions.

VALUE OF SUNLIGHT. “Sunlight is a most effectivp agent in the killing off process as is also the absence of moisture, which is essential for growth and multiplication. Free oxygen is essential for the growth of some bacteria; others will not develop in its presence, while some adapt them-

selves to either state, living in the absence or presence of oxygen. The limit of the optical possibilities of the ordinary microscope is almost reached with some of the known bacteria, but the latest ultra mietoscope methods have succeeded in demonstrating- what ap* pears to be the organisms of diseases hitherto of unknown origin. These particular organisms are referred to as filter passers, and are extremely minute. The name filter passers is given for the reason that these organisms are able to pass through the specially constructed filters which will hold back, or retain the known organisms—that is, the organisms which can be seen by the ordinary microscopic methods. ’ ’ ,