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Write in brief about growth curve of bacteria using suitable diagram

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bacterial growth curve lag log stationary death phases microbiology

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Bacterial growth curve

A bacterial growth curve shows the change in the number of viable bacteria with time when bacteria are grown in a closed liquid medium, called a batch culture. The vertical axis is plotted as the logarithm of viable cell count, and the horizontal axis represents time. It has four phases. OpenStax microbiology
Log number of
viable bacteria
     ^
     |                         _____________
     |                       /               \
     |                     /   Stationary     \
     |                   /       phase         \
     |                 /                         \
     |               /                            \  Death/
     |             /  Log (exponential)             \ decline
     |___________/       phase                        \____
     |  Lag phase
     +----------------------------------------------------> Time
  1. Lag phase
    • No increase in cell number.
    • Bacteria adapt to the new medium and synthesize enzymes, metabolites, and cell components needed for multiplication.
    • Its duration depends on the age of inoculum and difference between old and new media.
  2. Log or exponential phase
    • Bacteria divide at a constant maximum rate.
    • The population doubles at regular intervals, called the generation time.
    • Cells are metabolically most active and are generally most susceptible to antibiotics and disinfectants.
  3. Stationary phase
    • Nutrients become depleted and toxic metabolic products accumulate.
    • Rate of cell division equals rate of cell death, so the total viable count remains nearly constant.
    • Some bacteria may produce spores or secondary metabolites in this phase.
  4. Death or decline phase
    • Death rate exceeds multiplication rate.
    • The number of viable cells decreases, often exponentially.
The curve describes the behavior of the whole bacterial population, not the life cycle of an individual bacterium. Jawetz, Melnick & Adelberg’s Medical Microbiology, p. 63.

Create a labeled PDF diagram of the bacterial growth curve

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bacterial growth curve

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bacterial growth curve lag exponential stationary death phase educational diagram

Running Command

mkdir -p "/tmp/workspace/bacterial-growth-curve/output" && python -c "import matplotlib; print('matplotlib', matplotlib.__version__)"

Writing File

~/bacterial-growth-curve/create_diagram.py

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.backends.backend_pdf import PdfPages

out = '/tmp/workspace/bacterial-growth-curve/output/bacterial_growth_curve_labeled.pdf'

plt.rcParams.update({'font.family': 'DejaVu Sans'})
fig, ax = plt.subplots(figsize=(11.69, 8.27))  # A4 landscape
fig.patch.set_facecolor('white')
ax.set_facecolor('#fbfdff')

# Idealized batch culture curve with smooth phase transitions
x = np.linspace(0, 10, 700)
y = np.zeros_like(x)
# Lag: slight increase only
m1 = x < 1.8
y[m1] = 1.02 + 0.04 * (x[m1]/1.8)**2
# Exponential: steep rise, smoothly curved to plateau
m2 = (x >= 1.8) & (x < 4.9)
t = (x[m2]-1.8)/(4.9-1.8)
y[m2] = 1.06 + 5.05 * (3*t**2 - 2*t**3)
# Stationary: gentle plateau
m3 = (x >= 4.9) & (x < 7.1)
t = (x[m3]-4.9)/(7.1-4.9)
y[m3] = 6.11 - 0.10*t + 0.025*np.sin(np.pi*t)
# Death: decline
m4 = x >= 7.1
t = (x[m4]-7.1)/(10-7.1)
y[m4] = 6.01 - 3.85*(t**1.23)

ax.plot(x, y, color='#0B5FA5', lw=4.2, solid_capstyle='round', zorder=3)
ax.fill_between(x, 0.7, y, color='#CFE8F7', alpha=0.65, zorder=1)

# Phase bands
phases = [
    (0, 1.8, '#EAF4E1', 'LAG PHASE'),
    (1.8, 4.9, '#E8F2FC', 'LOG / EXPONENTIAL PHASE'),
    (4.9, 7.1, '#FFF4D6', 'STATIONARY PHASE'),
    (7.1, 10, '#FCE7E7', 'DEATH / DECLINE PHASE'),
]
for a, b, c, label in phases:
    ax.axvspan(a, b, color=c, alpha=0.55, zorder=0)
    ax.text((a+b)/2, 0.89, label, ha='center', va='bottom', fontsize=10.3,
            fontweight='bold', color='#334155')
    if a > 0:
        ax.axvline(a, color='#94A3B8', ls='--', lw=1.0, zorder=2)

# Annotations
box = dict(boxstyle='round,pad=0.38', fc='white', ec='#7A96AB', lw=1.1)
ax.annotate('Adaptation to new medium\nNo net increase in cell number', xy=(0.95, 1.05), xytext=(0.35, 2.15),
            fontsize=10, ha='left', va='center', bbox=box,
            arrowprops=dict(arrowstyle='->', color='#526D82', lw=1.3))
ax.annotate('Rapid binary fission\nConstant maximal growth rate', xy=(3.4, 4.2), xytext=(2.05, 6.9),
            fontsize=10, ha='left', va='center', bbox=box,
            arrowprops=dict(arrowstyle='->', color='#526D82', lw=1.3))
ax.annotate('Cell division = cell death\nNutrients decrease; wastes accumulate', xy=(5.9, 6.05), xytext=(5.05, 7.35),
            fontsize=10, ha='left', va='center', bbox=box,
            arrowprops=dict(arrowstyle='->', color='#526D82', lw=1.3))
ax.annotate('Cell death exceeds division\nViable count falls', xy=(8.7, 4.05), xytext=(7.45, 2.45),
            fontsize=10, ha='left', va='center', bbox=box,
            arrowprops=dict(arrowstyle='->', color='#526D82', lw=1.3))

ax.set_xlim(0, 10)
ax.set_ylim(0.7, 8.1)
ax.set_xticks([])
ax.set_yticks([1,2,3,4,5,6,7])
ax.set_yticklabels(['10¹','10²','10³','10⁴','10⁵','10⁶','10⁷'])
ax.set_xlabel('Time after inoculation', fontsize=13, fontweight='bold', labelpad=15)
ax.set_ylabel('Log viable bacterial count (CFU/mL)', fontsize=13, fontweight='bold', labelpad=15)
for spine in ['top','right']:
    ax.spines[spine].set_visible(False)
ax.spines['left'].set_linewidth(1.5)
ax.spines['bottom'].set_linewidth(1.5)
ax.grid(axis='y', color='#CBD5E1', lw=0.7, alpha=0.7)

fig.suptitle('Bacterial Growth Curve in Batch Culture', fontsize=20, fontweight='bold', color='#123B5D', y=0.96)
fig.text(0.5, 0.035, 'An idealized curve plotting the logarithm of viable bacterial cells against time.', ha='center', fontsize=10.5, color='#475569')
fig.text(0.5, 0.015, 'CFU/mL = colony-forming units per millilitre', ha='center', fontsize=9.3, color='#64748B')
plt.subplots_adjust(left=0.12, right=0.97, top=0.87, bottom=0.15)
fig.savefig(out, format='pdf', dpi=300, bbox_inches='tight')
plt.close(fig)
print(out)
Running Command

python "/tmp/workspace/bacterial-growth-curve/create_diagram.py" && python -c "from pypdf import PdfReader; p='/tmp/workspace/bacterial-growth-curve/output/bacterial_growth_curve_labeled.pdf'; r=PdfReader(p); print('pages:',len(r.pages)); print(r.pages[0].extract_text()[:600])" && ls -lh "/tmp/workspace/bacterial-growth-curve/output/bacterial_growth_curve_labeled.pdf"

bacterial growth curve labeled

PDF Document · PDF

Explain isolation and cultivation of anaerobic bacteria using anaerobic jar.

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