A study of the alkali-forming bacteria found in milk /

Abstract

Definition of the alkali-forming groups of bacteria 2 Cause of the alkaline reaction in milk 3 Sources of the alkali-forming bacteria 9 Morphology and growth 10 Sources of nitrogen 11 Fermentation of carbohydrates 12 Fermentation of alcohcls 17 Fermentation of salts of organic acids 19 Reduction of nitrates and nitrites 30 Arbitrary grouping of the alkali-forming bacteria from milk 33 Summary and conclusions 35 HISTORICAL REVIEW. Occasionally references to the alkali-forming bacteria are found in bacteriological literature. This group of bacteria has not received much attention, probably because under the ordinary conditions of plating their presence can not be detected, and as a consequence their* rather wide distribution has been overlooked. The fact that alkali-forming bacteria are often present in market milk in large numbers was first brought to the attention of the authors during some studies (1) 1 on the bacteriology of raw and pasteurized milk. At that time no suitable means were available for obtaining any exact figures on their numbers in market milk, so they were classed with the inert types of bacteria. Wolff (12) in a study of bacteria which developed in milk found nonliquefying short rods, colonies of which resembled those of the colon-aerogenes group. These organisms were strict aerobes which produced neither acid nor gas but turned milk alkaline without any other change. Shippen (10) also found organisms, in the milk supply of Baltimore, which gave an alkaline reaction in milk without peptonizing or coagulating it. He found that these organisms in cultural reactions closely resembled i The numbers in parentheses refer to " Literature cited " at end of bulletin. 104410°-19-Bull. 782 1 100 c. c. of milk. Citric acid in 100 c. c. of milk.

Some Strains in Search of a Genus--Corynebacterium, Mycobacterium, Nocardia or What?

“…acid from dulcitol, lactose, a-methyl-D-glucoside, or raffinose; utilization of lactate, malate, and succinate; failure to use mucate or oxalate ; sensitivity to methyl violet, pyronin, MacConkey agar, and penicillin ; and the oxidative utilization of glucose. All but one (~6 1 1 7 ) of the 97 cultures grew in the aerobic tube of Hugh & Leifson's medium and changed the indicator to the acid colour; all but ~6 1 1 7 formed acid from glucose in aerobic culture on the medium of Ayers, Rupp & Johnson (1919) ; and all cultures grew in the anaerobic tubes of both media but did not change the indicator to the acid colour.…”

“…Properties shared by these 36 strains were: failure to decompose casein, tyrosine, or xanthine; ability to hydrolyse starch; lack of growth at 52O; growth a t 35", 28*, and 10'; formation of acid from glucose; inability to produce acid from arabinose, dulcitol, inositol, lactose, mannitol, a-methyl-D-glucoside, raffinose, rhamnose, or sorbitol; utilization of lactate, malate, and succinate ; sensitivity to dyes, MacConkey agar, and penicillin; inability to deaminate phenylalanine ; and the oxidative utilization of glucose. All 36 cultures formed acid from glucose in aerobic culture on the inorganic nitrogen medium of Ayers et al (1919) and all but one (1157) formed acid in the aerobic tube of Hugh & Leifson's medium. All the cultures grew in the anaerobic tubes of both media but did not produce acid.…”

The Characterization of Pseudomonas fluorescens

“…In the absence of de-amination it was difficult to account for the alkaline reaction. The work of Ayers, Rupp & Johnson (1919) suggested an explanation, namely citrate utilization with concomitant bicarbonate formation. The milk agar plate method of testing was confirmatory : although the unmistakably proteolytic isolates effected the rapid formation of clear zones round the growth (not precipitated with acidified mercuric chloride) the intense alkali-producers gave no such indication of protein decomposition (occasional slight clearing disappeared on addition of the acidified mercuric chloride solution),…”

Biochemical and genetical analysis reveal a new clade of biovar 3 Dickeya spp. strains isolated from potato in Europe

“…It included growth at 39°C, 41°C and 25°C (control) on nutrient broth (NB, Oxoid) (Dye 1968), anaerobic hydrolysis of arginine (Moeller 1955), and polysaccharide inulin utilisation in phenol red peptone water (inulin extracts from chicory and dahlia were used at 0.3% final concentration). Eight carbon sources were tested by acidification/alkalisation on liquid Ayers, Rupp and Johnson medium (Ayers et al 1919) with bromothymol blue mixed with different 0.3% carbohydrates: (−)-D-arabinose, 5-keto-D-gluconate, mannitol, (+)-D-melibiose, (+)-D-raffinose and (−)-D-tartrate, β-gentiobiose and (+)-L-tartrate. The different basal media (150 µl) were dispensed on a sterile culture microplate (Greiner bio-one, Cellstar), and 15 µl of bacteria suspension of 10 8 cells ml −1 of each isolate to be analysed were added per well.…”