Document:

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                                                                    EXHIBIT 4(b)

                                AMENDMENT NO. ONE
                                     TO THE
                            ATMOS ENERGY CORPORATION
                     EMPLOYEE STOCK OWNERSHIP PLAN AND TRUST
                            EFFECTIVE JANUARY 1, 1999

         WHEREAS, ATMOS ENERGY CORPORATION (the "Company") has heretofore
amended and restated the Atmos Energy Corporation Employee Stock Ownership Plan
and Trust Effective January 1, 1999 (the "Plan"); and

         WHEREAS, pursuant to the provisions of Section 10.01 of the Plan, the
Company desires to amend the Plan in certain respects as hereinafter provided.

         NOW, THEREFORE, Atmos Energy Corporation does hereby amend the Plan,
effective as of January 1, 1999, as follows:

         1. Subsection 3.01(c) is amended by deleting the first sentence of such
subsection and replacing it with the following:

         The term "Entry Date" shall mean the first day of the first payroll
         period coincident with or immediately following each January 1st, April
         1st, July 1st, or October 1st.

         2. Subsection 3.05(b) is amended by striking paragraph (2) and
substituting the following paragraphs (2) and (3) and renumbering paragraph (3)
as paragraph (4):

                  (2) All amounts transferred from the United Cities Plan that
         are attributable to an Employee's employer matching contributions under
         the United Cities Plan shall be held in a subaccount of the Employer
         Contribution Account established for such Employee under the Plan; and

                  (3) All amounts transferred from the United Cities Plan that
         are attributable to an Employee's additional matching contributions
         under the United Cities Plan shall be held in a subaccount of the
         Employer Contribution Account established for such Employee under the
         Plan; and

         3. Subsection 4.01(e)(2) is amended by inserting the following sentence
at the end of such subsection:

         An amendment to a Participant's salary reduction agreement reducing his
         salary reduction to zero percent (0%) will not be deemed to be a
         termination of such Participant's salary reduction agreement.

         4. Section 4.03 is amended by adding the following at the end of said
         Section:

         Discretionary contributions credited to a Participant's Employer
         Contribution Account shall be one hundred percent (100%) vested and
         nonforfeitable at all times.

<PAGE>   2

         5. Subsection 5.03(a)(1) is amended by deleting such subsection and
replacing it with the following:

                  (1)      is $30,000 (or such greater amount as permitted under
                           Internal Revenue Service Rulings to reflect increases
                           in the cost-of-living); and

         6. Subsection 6.04(b)(1)(iii) is amended by adding at the beginning
thereof, the following: "Unless the Participant elects a later date (but not
later than the Participant's Required Beginning Date),".

         7. Subsection 6.04(b)(2) is amended by striking paragraph (B) of said
subsection and substituting in lieu thereof the following:

                  (B) The "Required Beginning Date" of a Participant who is not
         a five percent owner is the April 1 of the calendar year immediately
         following the later of (i) the calendar year in which he attains age
         seventy and one-half (70 1/2), or (ii) the calendar year in which he
         incurs a Severance from Service.

         8. Subsection 6.06(a)(1) is amended by deleting the first sentence in
such subsection and replacing it with the following:

         If the Participant elects a withdrawal from his Salary Reduction
         Contribution Account prior to the date on which he attains age 59-1/2,
         such withdrawal (i) may not include any earnings accrued after 1988 and
         (ii) will require the consent of the Committee.

         9. Subsection 6.06(a)(1)(c) is amended by deleting such subsection and
replacing it with the following:

                  the payment of tuition and room and board for the next twelve
                  (12) months of post-secondary education for the Participant,
                  the Participant's spouse, children or dependents; or

         10. Subsection 6.06(a)(1) is amended by inserting the following
paragraph at the end of such subsection, immediately before paragraph (2), and
renumbering paragraphs (2) and (3) as paragraphs (3) and (4):

         (2)      Withdrawals made from a Participant's Safeharbor Matching
                  Contribution Account may not occur on account of financial
                  hardship.

         11. Subsection 6.06(b) is amended by striking the first sentence of
said subsection and substituting in lieu thereof the following:

         On any January 1, a Participant may elect to withdraw any amount in his
         Employer Contribution Account or Matching Employer Contribution Account
         but only to the extent that such amount was allocated and paid to
         either such Account under this Plan (including amounts allocated under
         this Plan pursuant to Section 3.05 hereof) or the Prior Plan at least
         two (2) years prior to withdrawal; provided, however, that a
         Participant may withdraw any amount allocated to either such Account at
         any time such Participant properly demonstrates a financial hardship as
         described in Section 6.06(a)(1) hereof.

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<PAGE>   3

         12. The third sentence of Section 7.01 is amended by deleting such
sentence and replacing it with the following:

         Notwithstanding anything herein to the contrary and pursuant to ERISA
         Section 403(c)(2), upon an Employer's request, a contribution which was
         made by an Employer to the Plan by a mistake of fact or conditioned
         upon the deductibility of the contribution under Code Section 404,
         shall be returned to the Employer within one (1) year after the payment
         of the contribution or the disallowance of the deduction (to the extent
         disallowed), whichever is applicable.

         13. Subsection 7.02(i) is amended by striking the second paragraph of
said subsection and substituting in lieu thereof the following:

         Each person who is a Participant and is actively employed by an
         Employer on the date that a dividend is paid under clause (ii) above
         may elect to contribute such dividend to the Plan as an additional
         Salary Reduction Contribution under Section 4.01 hereof for the Plan
         Year in which such dividend is paid, subject to the limitations
         described in Sections 4.01(c) and 5.03 hereof, provided, however, that
         if such Participant does not so elect to contribute such dividend, such
         dividend shall be paid to such Participant in cash.

         14. Subsection 7.05(a) is amended by striking said subsection and
substituting in lieu thereof the following:

         (a)      In General. Notwithstanding the preceding provisions of this
                  Article VII, a Participant shall have the right, in accordance
                  with the provisions of this Section 7.05, to direct the
                  Trustee as to the investment of his Salary Reduction
                  Contribution Account and any rollover contributions and any
                  amounts in his United Cities employer matching contribution
                  subaccount pursuant to Section 3.05(b)(2) hereof (the "United
                  Cities Matching Subaccount"), held in his Employer
                  Contribution Account. Any such investment direction by a
                  Participant shall consist solely of the right to direct the
                  extent to which Salary Reduction Contributions, rollover
                  contributions and amounts in his United Cities Matching
                  Subaccount, if any, shall be invested in various investment
                  media comprising a Diversified Fund. Such investment
                  directions shall be made in accordance with procedures
                  established by the Committee. Should a Participant fail to
                  provide the Trustee with the investment directions described
                  herein as to any Salary Reduction contribution or rollover
                  contribution or amounts in his United Cities Matching
                  Subaccount, such contribution or amount shall be invested in
                  Company Stock.

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<PAGE>   4

         15. Subsection 7.06(a) is amended by deleting paragraph (4) and
replacing it with the following:

         (4)      the default provisions of the promissory note which evidences
                  each loan must prohibit offset of the Participant's account
                  balance under this Plan prior to the time that the Participant
                  has a Severance From Service or the Trustee otherwise would
                  distribute the Participant's account balance under the Plan.

         IN WITNESS WHEREOF, the Company has caused this AMENDMENT NO. ONE TO
THE ATMOS ENERGY CORPORATION EMPLOYEE STOCK OWNERSHIP PLAN AND TRUST EFFECTIVE
JANUARY 1, 1999 to be executed in its name on its behalf this 1st day of August,
2000, effective as of January 1, 1999.

                                   ATMOS ENERGY CORPORATION

ATTEST:
                                   By: /s/ ROBERT W. BEST
                                       ------------------------------------
                                       Robert W. Best
                                       Chairman of the Board, President and
                                       Chief Executive Officer
-----------------------------

                                   TRUST COMMITTEE

ATTEST:
                                   By: /s/ DON P. BURMAN
                                       ------------------------------------
                                       Don P. Burman

-----------------------------
                                   By: /s/ GARY L. SCHLESSMAN
                                       ------------------------------------
                                       Gary L. Schlessman

                                   By: /s/ RONALD W. MCDOWELL
                                       ------------------------------------
                                       Ronald W. McDowell

                                   By: /s/ WYNN D. MCGREGOR
                                       ------------------------------------
                                       Wynn D. McGregor

                                   By: /s/ GORDON J. ROY
                                       ------------------------------------
                                       Gordon J. Roy

                                       4<PAGE>   1
                                                                    EXHIBIT 4(c)

                                AMENDMENT NO. TWO
                                     TO THE
                            ATMOS ENERGY CORPORATION
                     EMPLOYEE STOCK OWNERSHIP PLAN AND TRUST
                            EFFECTIVE JANUARY 1, 1999

         WHEREAS, ATMOS ENERGY CORPORATION (the "Company") has heretofore
amended and restated the Atmos Energy Corporation Employee Stock Ownership Plan
and Trust Effective January 1, 1999 (the "Plan"); and

         WHEREAS, pursuant to the provisions of Section 10.01 of the Plan, the
Company desires to amend the Plan in certain respects as hereinafter provided.

         NOW, THEREFORE, Atmos Energy Corporation does hereby amend the Plan,
effective as of June 1, 2000, except as otherwise provided herein, as follows:

         1. Effective as of January 1, 2001, Section 2.01(i) is amended by
adding the following at the end of paragraph (1) of said Section:

         Notwithstanding any other provision of this Plan, Compensation shall
         include any and all lump sum merit payments made to such Participant by
         an Employer.

         2. Section 2.01(l) is amended by adding the following at the end of
paragraph (1) of said Section:

         Those individuals shall include employees of Southwestern Energy
         Company ("SEC") and/or Arkansas Western Gas Company ("AWGC") who became
         Employees of an Employer as a result of the Company's acquisition of
         certain assets associated with the Associated Natural Gas operations of
         SEC and AWGC (such individuals are referred to herein as "ANG
         Employees").

         3. Section 2.01(m) is amended by adding the following at the end of
said Section:

                  Said account shall include amounts transferred from the
         Southwestern Energy Company 401(k) Savings Plan (the "SEC Plan") on
         behalf of ANG Employees which are attributable to after-tax
         contributions as provided for in Section 3.06 hereof.

         4. Section 2.01(o) is amended by adding the following at the end of
said Section:

                  Said account shall include amounts transferred from the SEC
         Plan on behalf of ANG Employees which are attributable to rollover
         contributions and employer matching contributions as provided for in
         Section 3.06 hereof. Said account shall also include all amounts
         received by a Participant as matching contributions, and adjustments
         relating thereto under the Prior Plan.

         5. Section 2.01(y) is amended by deleting said Section in its entirety
and substituting in lieu thereof the word "Reserved".

<PAGE>   2

         6. Section 2.01(hh) is amended by adding the following at the end of
said Section:

                  Said account shall include amounts transferred from the SEC
         Plan on behalf of ANG Employees which are attributable to salary
         reduction contributions as provided for in Section 3.06 hereof.

         7. Article III is amended by adding the following Section 3.06 at the
end of said Article:

         3.06     Special Rules for ANG Employees

         (a)      For purposes of eligibility to make salary reduction
                  contributions under Section 4.01, ANG Employees (as defined in
                  Section 2.01(l) hereof) shall be eligible to participate in
                  this Plan as of the first day of the first payroll period
                  coincident with or immediately following June 1, 2000. For
                  purposes of eligibility to receive allocations of safe harbor
                  matching contributions under Section 4.02 and discretionary
                  contributions under Section 4.03, an ANG Employee shall be
                  eligible to participate in this Plan as of the Entry Date
                  coincident with or immediately following his completion of one
                  (1) Year of Service. For purposes of Section 3.02, ANG
                  Employees shall be credited with Service equal to their
                  service credited under the SEC Plan (as defined in Section
                  2.01(m) hereof).

         (b)      The account balances of ANG Employees who were participants in
                  the SEC Plan which are transferred into the Plan effective as
                  of June 1, 2000, shall be held, administered, and distributed
                  as part of the Plan as follows:

                  (1)      All amounts transferred from the SEC Plan that are
                           attributable to an ANG Employee's salary reduction
                           contributions under the SEC Plan shall be held in the
                           Salary Reduction Contribution Account established for
                           such Employee under the Plan;

                  (2)      All amounts transferred from the SEC Plan that are
                           attributable to an ANG Employee's after-tax
                           contributions, if any, under the SEC Plan shall be
                           held in the Employee Contribution Account established
                           for such Employee under the Plan. The ANG Employee
                           shall be 100% vested in said Account.

                  (3)      All amounts transferred from the SEC Plan that are
                           attributable to an ANG Employee's rollover
                           contributions, if any, under the SEC Plan shall be
                           held in a subaccount of the Employer Contribution
                           Account established for such Employee under the Plan.
                           The ANG Employee shall be 100% vested in said
                           subaccount.

                  (4)      All amounts transferred from the SEC Plan that are
                           attributable to an ANG Employee's employer matching
                           contributions under the SEC Plan shall be held in a
                           subaccount of the Employer Contribution Account
                           established for such Employee under the Plan. The ANG
                           Employee shall be 100% vested in said subaccount and
                           all amounts contained therein may be invested
                           immediately.

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<PAGE>   3

                  (5)      All stock transferred from the SEC Plan that is
                           Entergy stock shall be held in a separate investment
                           fund called the Entergy Stock Fund established for
                           such Employee under the Plan. All amounts contained
                           in the Entergy Stock Fund may be invested in other
                           investments as provided for in Section 7.05(d).

         (c)      For purposes of Section 3.01(c), the Entry Date for ANG
                  Employees who have completed one (1) Year of Service as of
                  June 1, 2000, after taking into account the provisions of
                  Section 3.06(a) hereof, shall be the first day of the first
                  payroll period coincident with or immediately following June
                  1, 2000.

         (d)      All outstanding loans of the ANG Employees under the SEC Plan
                  shall be transferred in kind to the Plan and shall be
                  maintained and administered under Section 7.06 in accordance
                  with the terms of said loans as in effect at the time of said
                  transfer.

         8. Effective as of January 1, 2001, Section 4.01(e)(2) is amended by
striking said Section and substituting in lieu thereof the following:

                  (2) A salary reduction agreement may be entered into or
         amended or terminated by a Participant at any time upon notice to the
         Committee, subject to the requirements of paragraph (3), below. If a
         Participant terminates his salary reduction agreement, he may enter
         into another salary reduction agreement at any time thereafter, subject
         to the requirements of paragraph 3, below.

         9. Section 5.01 is amended by striking the third sentence of said
Section and substituting in lieu thereof the following:

         When appropriate, a Participant shall have four separate accounts, an
         Employer Contribution Account, a Salary Reduction Contribution Account,
         a Safe harbor Matching Contribution Account, and an Employee
         Contribution Account.

         10. Section 5.04(a)(1) is amended by striking said subsection and
substituting in lieu thereof the following:

         (1)      the value of the sum of Employer Contribution Accounts, Salary
                  Reduction Contribution Accounts, Safe harbor Matching
                  Contribution Accounts, plus Employee Contribution Accounts
                  (but not including any allocations to be made as of such last
                  day of the Plan Year except contributions actually made on or
                  before that date and allocated pursuant to Sections 5.02(b)
                  and (c)) of Participants who are Key Employees (as defined
                  below) exceeds 60% of the value of the sum of Employer
                  Contribution Accounts, Salary Reduction Contribution Accounts,
                  Safe harbor Matching Contribution Accounts, plus Employee
                  Contribution Accounts (but not including any allocations to be
                  made as of such last day of the Plan Year except contributions
                  actually made on or before that date and allocated pursuant to
                  Sections 5.02(b) and (c)) of all Participants and their
                  Beneficiaries (the "60% Test"), or (2) the Plan is part of a
                  required aggregation group (within the meaning of Code Section
                  416(g)(2)) and the required aggregation group is top-heavy.
                  However, and notwithstanding the results of the 60% Test, the
                  Plan shall not be considered a Top-Heavy Plan for any Plan
                  Year in which the Plan is a part of a required or permissive
                  aggregation

                                       3
<PAGE>   4

                  group (within the meaning of Code Section 416(g)(2)) which is
                  not top-heavy. For purposes of the 60% Test for any Plan Year,
                  (i) the value of the Employer Contribution Accounts, Safe
                  harbor Matching Contribution Accounts, Salary Reduction
                  Contribution Accounts, and Employee Contribution Accounts of
                  individuals who are former Key Employees shall not be taken
                  into account and (ii) the value of the Employer Contribution
                  Accounts, Safe harbor Matching Contribution Accounts, Salary
                  Reduction Contribution Accounts, and Employee Contribution
                  Accounts of individuals who have not performed services for an
                  Employer for the five (5)-year period ending on the
                  determination date shall not be taken into account.

         11. Section 6.04(e) is amended by adding the following at the end of
said Section:

                  In addition, notwithstanding the preceding provisions of this
         Section 6.04, Participants who are ANG Employees with account balances
         transferred from the SEC Plan may elect to receive distribution of
         their benefits (i) in monthly installments over a period equal to the
         shorter of one hundred twenty (120) months or the applicable life
         expectancy of the Participant or the Participant's spouse, or (ii) in
         installment payments of a fixed amount, such payments to be made until
         exhaustion of the Participant's Account balances under the Plan.

         12. Section 6.06(b) is amended by striking said subsection and
substituting in lieu thereof the following:

         From Employer Contribution Account or Matching Employer Contribution
         Account. On any January 1, a Participant may elect to withdraw any
         amount in his Employer Contribution Account, but with respect to the
         amounts in such Account attributable to Discretionary Contributions
         made pursuant to Section 4.03 hereof and amounts allocated to such
         Account under this Plan pursuant to Section 3.05(b)(2) and 3.06(b)(4)
         hereof, only to the extent that such amounts were allocated and paid to
         such Account under this Plan or the Prior Plan at least two (2) years
         prior to withdrawal. A Participant may withdraw any amount allocated to
         either his Employer Contribution Account or his Matching Employer
         Contribution Account at any time if such Participant properly
         demonstrates a financial hardship as described in Section 6.06(a)(1)
         hereof. A Participant shall not cease to be a Participant under the
         Plan solely because a distribution is made to such Participant pursuant
         to this Section 6.06(b). Withdrawal elections shall be made by the
         Participant on written forms provided by the Committee for that
         purpose.

         13. Subsection 7.05(a) is amended by striking said subsection and
substituting in lieu thereof the following:

         (a)      In General. Notwithstanding the preceding provisions of this
                  Article VII, a Participant shall have the right, in accordance
                  with the provisions of this Section 7.05, to direct the
                  Trustee as to the investment of (i) his Salary Reduction
                  Contribution Account, (ii) any rollover contributions, any
                  amounts in his United Cities Plan employer matching
                  contribution subaccount pursuant to Section 3.05(b)(2) hereof
                  other than amounts attributable to United Cities Plan
                  additional matching contributions (the "United Cities Plan
                  Matching Subaccount") and any amounts in his SEC Plan rollover
                  contribution subaccount and SEC Plan employer matching
                  contribution subaccount pursuant to Section 3.06(b)(3) and
                  Section 3.06(b)(4) hereof (the "SEC Plan Rollover and Matching
                  Subaccounts"),

                                       4
<PAGE>   5

                  held in his Employer Contribution Account, and (iii) any
                  amounts in his Employee Contribution Account attributable to
                  SEC Plan after-tax contributions pursuant to Section
                  3.06(b)(2) hereof (the "SEC Plan Employee Contribution
                  Account"). Any such investment direction by a Participant
                  shall consist solely of the right to direct the extent to
                  which Salary Reduction Contributions, rollover contributions,
                  amounts in his United Cities Plan Matching Subaccount, if any,
                  amounts in his SEC Plan Rollover and Matching Subaccounts, if
                  any, amounts in his SEC Plan Employee Contribution Account, if
                  any, shall be invested in various investment media comprising
                  a Diversified Fund. Such investment directions shall be made
                  in accordance with procedures established by the Committee.
                  Should a Participant fail to provide the Trustee with the
                  investment directions described herein as to any Salary
                  Reduction contribution or rollover contribution or amounts in
                  his United Cities Plan Matching Subaccount, amounts in his SEC
                  Plan Rollover and Matching Subaccounts, if any, and amounts in
                  his SEC Plan Employee Contribution Account, if any, such
                  contribution or amount shall be invested in Company Stock.

         14. Section 7.05 is further amended by adding a new subsection 7.05(d)
at the end of said Section as follows:

         (d)      Entergy Stock Fund. Notwithstanding the foregoing provisions
                  of this Section 7.05, a Participant for whom amounts are
                  invested in the Entergy Stock Fund provided for under Section
                  3.06(b)(5) may direct that all or any portion of such amounts
                  be invested in a Diversified Fund or in Company Stock in
                  accordance with the procedures established by the Committee;
                  however, no additional amounts may be invested in the Entergy
                  Stock Fund. Furthermore, amounts in the Entergy Stock Fund are
                  not subject to the Company Stock default investment provided
                  for in the preceding subsections of this Section 7.05.

         IN WITNESS WHEREOF, the Company has caused this AMENDMENT NO. TWO TO
THE ATMOS ENERGY CORPORATION EMPLOYEE STOCK OWNERSHIP PLAN AND TRUST EFFECTIVE
JANUARY 1, 1999 to be executed in its name on its behalf this 31st day of May,
2001, effective as of June 1, 2000.

                                       ATMOS ENERGY CORPORATION

ATTEST:
                                       By: /s/ ROBERT W. BEST
                                           ------------------------------------
                                           Robert W. Best
                                           Chairman of the Board, President and
                                           Chief Executive Officer
---------------------------------

                                       TRUST COMMITTEE

ATTEST:
                                       By: /s/ LAURIE M. SHERWOOD
                                           ------------------------------------
                                           Laurie M. Sherwood

---------------------------------

                                       5
<PAGE>   6

                                       By: /s/ TOM S. HAWKINS, JR.
                                           ------------------------------------
                                           Tom S. Hawkins, Jr.

                                       By: /s/ RONALD W. MCDOWELL
                                           ------------------------------------
                                           Ronald W. McDowell

                                       By: /s/ WYNN D. MCGREGOR
                                           ------------------------------------
                                           Wynn D. McGregor

                                       By: /s/ GORDON J. ROY
                                           ------------------------------------
                                           Gordon J. Roy

                                       6

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