Taxonomy is a significant aspect

-of study, for a microbiologist, in any

application. But, the problems are

greater for an aquatic microbiologist

as compared to those of a medical

microbiologist, because studies have

been made in depth in medical microbiology

Pillai, C Thankappan

CMFRI Digital Repository

• @ Fish and Shellfish Diseases m Culture Systems IX Screening of bacteria for identification C. Thankappan Pillai Central Marine Fisheri es Research Institute. Cochin - 18. Taxonomy is a significant aspect -of study, for a microbiologist, in any application. But , the problems are greater for an aquatic microbiologist as compared to those of a medical microbiologist, because studies have been made in depth in medical micro-biology. For identifying bacteria , various systems of classification exist (Scholes and Shewan , 1964). A very detailed and useful key is provioed by Buchanan and Gibbons (1974). However. pro-blems still exist in this system of clas-sification. It is good that the number of species has been reduced in the 8th edition of Bergey's Determinative Bacteriology. For example, where there were'6 species in the genus, Micro-COCCUS in the 7th edition of Bergey's, in the 8th edition there appear only three species in the genus. Micrococcus. As a result, one has to fix one's isolate within this number of avail-able species which mostly results in the repetition of the same species. In addition to this. Bergey's system of classification can be handled only by specialists. In order to aid beginners in micro-bial taxonomy. a simple and rapid system is called for and this has led to the formation of the key, given in Tables 1 and 2 for screening bacteria: rods and cocci (plate 1: fig. 1 and 2). The present keys require the follow-ing tests for categorising an organism. 1) Cell morphology and Gram's staining according to Hucker's modification (Bullock, 1971). 2) Motility in hanging drop prepara-tions from cultures following inoculation for 6-18 hours in July 1982 peptone water or sea wate r peptone (1 :" peptone in aged and filtered sea water pH 2-7.5). 3) Sensitivity to 2.5 I.U . of penicillin and '0/129' (Shewan eta/., 1954). (1 mg. of Pencil lin is 1667 I.U) . 4) Breakdown of glucose (Hugh and Leifson, 1953). 5) Oxidase according to Kovacs (1965} 6) Haemolysis in blood agar (cooled! sterile nutrient agar plus 5% sterile defibrinated blood). 7) Oxygen relationship (Mackie and McCartney, 1962). 8) Coagulase (Mackie and McCartney. 1962) . 9) Cellu lose digestion (Skerman,1959). 10) Acid and gar production in peptone water including respective sugar with Andrade's indicator (Crui-ckshank ,t a/" 1975) . 11) Pigmentation in milk agar. If the disease is suspected to be tuberculosis, inoculate the sample in glycerol agar (Nutrient agar plus 1%. glycerol) and incubate at room tem-perature form a few days upto 2 weeks. Colony characters may be noted if Gram positive, acid fast organism is observed. The organism may be tentatively classified , based on the pigment. as Mycobacterium marinum if the pigment is photochromogenic and M. fortuitum-if there is no pigment. '0/129' =2,4 · Diamino - 6, 7-diisopropyl pteridine 27 C/l (1) '" -o o 0. m x "C o -c... o c: :; 2!. I + I + Spores I Bacillus sp. ----(Basillosis) With I TABLE BACTERIA (RODS) I GRAM 'S STAINING I I Short rods I Coryn ebac terium sp. (Kidney Diseases) Long thin rod s Flexibac ter / Cytophaga SP. ( Myxobac terio sis) Sensitivity to penicillin (2 .5 i.u) i I Breakdown of glucose I + I I I Pigment No pigm ent Flavobacterium sp. Alcalig enes sp. (F lavobacteriosis) (Alaca l igenosis) I I Fermentative Non ferment ative I I I I I gas but insensitive without gas but sens it ive Kovacs' oxidase to '0 /129' to '0/129' I Vibrio sp. Motility (VIBRIOSIS) I I----------------~~ I Motile Aeromona~ sp. (Hemorrhagic Septicemia) Non motile Aeromonas sa lmonicid 3 (Furunculosis) + Pseudomonas sp. (H emorrhagic Septicemia) Enterobacte ri aceae (Enteric Bacteriosis) '0/129' = 2.4 6,7 diisopropyl pteridine L c: -< ~ CD co N I Motile Planococcus sp. 'fABLE II BACTERIA + (GRAM COCCI) I Moti l ity I I Non motile Brekdown of glucose I I I Fermentative Non fermentative I I I I I Haemolytic cells Mayor may not be haemolytic. Mayor may not be haemolytic. I in chains cells in irregular clusters cells in packets of eight Oxygen re lation Streptococcaceae I Sarcina sp. I I Haemolytic cells In chains Streptococcus sp. I Coagulase I + Staphylococcus aureus I . Non haemolytic lenti eu lar cells Leuconostoc sp. I Aerobic Micrococcus sp. (M icrococcosis) I Anaerobic Peptococcacae (Except the genus, Sarcina) I I Staphylococcus epidermidis OR Staphylococcus saprophyticus + Cellulose digestion I I eells in pair or in tetrads Pediococcus sp. Ruminococcus sp. I In chain Peptostreptcoccus sp. Cell arrangement I Not in chain Peptococcus sp. I I cell in tertrads Haemolytic cells of flattened adjacent sides Aerococcus viridan s Gemella sp. t;5 (Streptococcosis) (Aerococcosis) 

Fish and shellfish diseases in culture systems IX Screening of bacteria for identification

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Fish and shellfish diseases in culture systems IX Screening of bacteria for identification

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