THE AGKICULTURAL NEWS. 



Mai:. 



i9i: 



THE NATURE OJ^ BACTERIA. 



(.'..nsideruig thati roference is continually 

 Le-ny made in these columns to bactena ot 

 otif kind or another, the follosnng gen-'tai description 

 of th.ir nature. bv -Mr. 1». K. .Jones, B8.A.. Protessor 

 vi KicteiiolocTN-. < intario Asricaltiiriii Coiloge, published 

 a.< BxiJlclir- >"'■' oi the ( inlaiio DepaJ-tment of Airncul- 

 tme, will doubtless be of int' vestto onr rea.iers:— 



('.fteria are microscopic \,\xrH. Tliey are the smallest 

 ionns of lite known, and in order to 9«e thera it is necessary 

 f» u-se Afee .Jiighest power Inicl•o^5eope, together with other 

 haateriologicftl apparatus. Some species ot bacteria are so 

 infimtely . fsiiiall tiiat they can be only just discerned even 

 ^vltil thehigUfst inagnifyini? inicn ".scopes, and it is considered 

 rliat there "are some wiiich arc even still auallcr, being too 

 email to coiuf withiu our range of vision ^vith all the aidt^ 

 known to scienc<>. Jl'he avewgc^^'.e-of the more common species 

 of bacteria i* aV.mt 1 lO.OVui of an inch in length and 

 1 '20,0<X) of an inch in breath. 



In addition to 'heihg the smallest of living thing.?, bacteria 

 are the simple^ «l living thi'iigs in their structure. They are 

 ■uoicellulai, that is, their whc-b body consists of only one cell. 

 The bacterial cell is composed of protoplasm enclosed in a 

 meinbrane, and the whole (.ell is transparent. 



• There 31*6 four typical shapes of bacteria; (I5 .spherical 

 iorms known as cocci:(2) ^trstight rod forms knowrl as bacilli. 

 •(3) spiral forms known as spirilla; -and {4/ thread form.s known 

 as thread bacteria, l^cteria of any ot tht^se four types never 

 change to either of the other types. Thereare many species of 

 each type. • -i 



Bacteria absorb their fot«i in solution through their cell 

 membrin'-. The food so absorbed is utilized by the internal 

 prouiplasm ,ot the cell, which thus increa.'^es in ijuantity, and 

 following this increase in aubstnuce the cell divides in two, 

 each cell being a complete bacterium. ^ These two bacteria 

 continuing 10 feed, again divide, and thus product- four, .and 

 80 the development and innltip|icalion goes -^on. Under 

 favourdble conditions of moi.siuro; food, and -<vartiith this 

 growing and dividing take.s place aboutevery EVtnty minutes 

 or half hour, so that in twonty-four hours we may get 

 a progeny of .ten to twenty millions of bacteria, all 

 ileveiopci from one bact<erial cell It is this power of rapid 

 multiplication, inducing as it doe< changes in the material in 

 which the bacteria are growing, that uiake.s bactbria so 

 iniportant in the economies of life, some of thirm being 

 beaeticial and gotne injurious. "' 



Some species r.f bacteria have the power of motion when 

 placed in li<(ui<-Ls. Some of them move about like fish, others, 

 wriggle like mosquito larvae, others glide .ilong with a snake- 

 like motion. These movemeuts can readily be (jbscrved when 

 a satiBfactory prei.araliou is viewed under the liigli power' 

 miciOKoope. The Vjacteria which-liave thia'power of motion are 

 furnished with delicate litth- whips called tlagelU. These 

 flagella [iroject from the body, sometimes from the ends and 

 soraetiinf* from the .-ndes, ari.i by waving or lasbjng these 

 Hagolk the bacterm are propelle.i forward or backward 



Some species of bacleria, when tlie food supply fails them 

 or bccoiueti otherwise unfavouiablf!, go into, what is known as 

 the spore condition That in, the protoplasm within the cell 

 menibrane ajntia-U-;, and cuiiJfnseJ, and around this^tondensed 

 jirotoplasm another membraoeis (.ro-luced-.-wbich is very loiiglr 

 and icaistant. This condcnsrd protoplaam, encloi'ed in its 

 tQlii/h mernbrane, is the bacterial spore- The.''i« banii-riAl 



spores are very resistant' to drying, heat, and di.-iinfectant 

 Some of them may be boiled for an hour or two without being 

 killed. It is the pre.^ence of .such bacterial spores on meat 

 and vegetables such as corn, peas, bean.s, etc., which makes- 

 it so difficult to presirve these materials satisfactorily. The- 

 spores remain dormant until the ronditions around thera are , 

 satisfactory for germination. Moisture, warmth, and food are 

 the conditions which induce germination of the spores. 

 When a spore germinates the membrane round it breaks oS 

 and the "rotoplasm emerges and forms a growing bacterial 

 cell. Thi> bacterial cell grows an^l maltl{>lies until conditions 



again b i 1; unfavourable for further multiplication, and theti 



the bad • rial cells thus formed go into the spore condition. 

 These bacterial spores are very common in soil, dust, and on 

 the surface of anything that is exposed to a dusty atmosphere. 



Some .species of bacteria produce soft, gelatinous capsules 

 around the outside of their membrane. It is these bacleria 

 which produce thi' so-called ropine.-ss in Uiilk and bread. 

 This ropintss is due to the development in the milk or bread 

 of large numbers of bacteria with their cajisules, and it is .the 

 sticking together of the capsules that maki-s the jxiilk or bread 

 ropy, slimy, and .sticky. The gelatinous substance which 

 grows on vinegar, and is known as mother of vinegar, 

 is simply a mass of millions of vinegar bacteria, each one with 

 its gelatinous capsule sticking to its neighbour. 



Bacteria are found in large number.s wherever any othei- 

 forms bf life exist. ( )rie ounce of cultivated .^oil will contain 

 millions of them in an active, growing condition. Jn dust, 

 they are present, u.«ually in the spore or dormant condition- 

 In natural waters such as rivers, lakes, poi! is. wells, etc., they 

 will be present in varying numbers according to the 

 amount of contamination from soil surface washings' and 

 seepage. They are present in immense numbers iii all 

 decaying or putrifying organic material, whether of 

 vi^getable or animal 6rigin, manure piles, garbage heaps, 

 etc. It is their presence and activities in such material 

 which induce the fermentation, decay, or putrefaction 

 which takes place. They are present on dry hay and 

 straw in considerable numbers, usually in the spore- 

 condition- Thej' are present on the hand.s, face, head, and 

 surface of the human body geuerally, and in imtnense; 

 numbers on the bodies of all animals, Hies, and other in.sects. 

 Any food material, whetjber cooked or uncooked, which ia 

 exposed, gets contaminated with them. As a result of-this^ 

 contamination the food is apt to spoil unless it is used before 

 it has time to de<";iy. ,Milk becomes sour or putrid as a 

 result of the development and multiplication of the b icteria 

 which get into it dnring the milking operations and subse- 

 rpicnt handling It may be said, therefore, that bacteria are 

 piactically present everywhere. 



Just as there are many kinds or species of higher plants 

 and anim'ids. so there are many species ot" bacteria. 

 Fortunately, the great majority of the species .are beneficial 

 in their action: some, however, are injurious, amongst which 

 are tho.su species which produce infi-ctioii^ disease* of' men 

 and animals, sncli as tuberculosis, tyjihoid fever, .jnthras, 

 etc., and those which produce diseases of phmt.H, A ilifi'etent 

 species of bacteria is necessary to j)roduce each of ' these 

 diseases. 



• In addition to those bacteria which .ard iojiirious. a» 

 causing disease, there are some which are beneficial in one |ilace 

 but injurious in another. Kor instance, many of the species- 

 o( bacteria beneficial iri the soil are injurious when tliey gel. 

 <m to food material, as they briAg' about the decay or pii'tre- 

 actiott of th¥ fooil. ret^dering' it >i'rifit ffir use if they at» 

 allowed to (ievcloi) ir.\ moltipiv on or in it- 



