H. LAXMINARAYANA et al
43
produced very high amounts of volatile acidity in milk (25 to 33 ml. of N/10 NaOH
per 250g. of culture) and fermented pentoses strongly, they were originally considered
to be related to S. paracitrovorous (Leuconostoc), but their inability to produce gas
from glucose, form acetoin from citrate in the absence of glucose or other source
of carbohydrate [Campbell and Gunsalus, 1944] and produce amonia from arginine
precluded their being placed in this category. On the other hand, they resembled
the Enterococcus group more closely (particularly S. liquefaciens) in their ability to
grow at high temperatures, resistance to pasteurisation (63°C. for 30 minutes) and
their tolerance to alkaline pH, 6.5 per cent NaCl and 0.1 per cent methylene blue.
S. liquefaciens has been reported to lose its proteolytic character and this organism
as well as S. faecalis have been reported to produce volatile acidity in milk [Long
and Hammer, 1936; Davis et al., 1939]. These isolates may therefore be regarded as
heterofermentative variants of S. faecalis or S. liquefaciens or they may form a distinct
species in the Enterococcus group of streptococci.
Lactobacilli. The lactobacilli have been classified (Tables IV a and 6) into six
different species, viz., L. bulgaricus (7 isolates), L. lactis (3 isolates), L. helveticus
(2 isolates), L. casei (4 isolates), L. plantarum (3 isolates) and L. fermenti (3 isolates).
The isolates included under the first three species (Thermobacteria) were character-
ized by their ability to grow at 50°C., failure to grow at 15°C., resistance to pasteuri-
sation (63°C. for 30 minutes) and rapid acid production and coagulation of milk in
13 to 40 hours at 37°C. Yeast dextrose milk was curdled in 6 to 10 hrs. at 45°C.,
and, with the exception of L. bulgaricus strains, all the isolates reduced litmus. The
maximum acidity ranged from 1.7 to 2.2 per cent lactic acid. They formed a firm
and highly acid curd with very little whey separation or volatile acid production
and did not produce gas from glucose or show growth in 2 per cent lactate media.
Their growth was not inhibited by 5 per cent NaCl but results regarding tolerance to
2.5 per cent NaCl and 0.1 per cent methylene blue were variable. All of them
fermented dextrose and lactose vigorously. Their further differentiation was
mainly based on slight morphological variations, their ability to reduce litmus, and
differences in the fermentation of sugars particularly of maltose and sucrose.
The strains of L. bulgaricus appeared as long slender rods (3.0-4.5X0.5-0.7µ)
usually occurring singly and occasionally in long chains or filaments, showing
metachromatic granules prominently when stained with aqueous methylene blue.
Agar colonies of these organisms were of the rough type and were highly filamentous.
Isolates L.96, L.393 and L.409 may be considered to be typical of the species except
for their tolerance to 2.5 per cent NaCl and fermentation of arabinose; L.96 had
the ability to ferment maltose slightly. One isolate (L.1) fermented arabinose and
sucrose strongly and maltose slightly. These organisms appeared to be analogous
to the lactobacilli associated with Yoghourt, Kefir and other fermented milks of the
Mediterranean and Middle East countries although the very high values of acidity
(2.5-4 per cent) reported by previous workers [Hammer, 1948] were not obtained
with them. They are probably similar to the organisms described by Chatterjee
[1910] under the name 'Streptothrix dadhi' and later by Ram Ayyar [1928].
Three isolates (L.326, L.376 and L.395) have been identified as L. lactis mainly
on account of their ability to reduce litmus and ferment sucrose, maltose, arbinose
and other sugars which are not attacked by L. bulgaricus. Morphologically they
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